diff --git a/bayesflow/diagnostics/plots/calibration_ecdf.py b/bayesflow/diagnostics/plots/calibration_ecdf.py
index d39d225a8..915687818 100644
--- a/bayesflow/diagnostics/plots/calibration_ecdf.py
+++ b/bayesflow/diagnostics/plots/calibration_ecdf.py
@@ -1,6 +1,7 @@
-from collections.abc import Mapping, Sequence
+from collections.abc import Callable, Mapping, Sequence
 
 import numpy as np
+import keras
 import matplotlib.pyplot as plt
 
 from ...utils.plot_utils import prepare_plot_data, add_titles_and_labels, prettify_subplots
@@ -13,6 +14,7 @@ def calibration_ecdf(
     targets: Mapping[str, np.ndarray] | np.ndarray,
     variable_keys: Sequence[str] = None,
     variable_names: Sequence[str] = None,
+    test_quantities: dict[str, Callable] = None,
     difference: bool = False,
     stacked: bool = False,
     rank_type: str | np.ndarray = "fractional",
@@ -78,6 +80,18 @@ def calibration_ecdf(
     variable_names    : list or None, optional, default: None
         The parameter names for nice plot titles.
         Inferred if None. Only relevant if `stacked=False`.
+    test_quantities   : dict or None, optional, default: None
+        A dict that maps plot titles to functions that compute
+        test quantities based on estimate/target draws.
+
+        The dict keys are automatically added to ``variable_keys``
+        and ``variable_names``.
+        Test quantity functions are expected to accept a dict of draws with
+        shape ``(batch_size, ...)`` as the first (typically only)
+        positional argument and return an NumPy array of shape
+        ``(batch_size,)``.
+        The functions do not have to deal with an additional
+        sample dimension, as appropriate reshaping is done internally.
     figsize           : tuple or None, optional, default: None
         The figure size passed to the matplotlib constructor.
         Inferred if None.
@@ -120,6 +134,36 @@ def calibration_ecdf(
         If an unknown `rank_type` is passed.
     """
 
+    # Optionally, compute and prepend test quantities from draws
+    if test_quantities is not None:
+        test_quantities_estimates = {}
+        test_quantities_targets = {}
+
+        for key, test_quantity_fn in test_quantities.items():
+            # Apply test_quantity_func to ground-truths
+            tq_targets = test_quantity_fn(data=targets)
+            test_quantities_targets[key] = np.expand_dims(tq_targets, axis=1)
+
+            # # Flatten estimates for batch processing in test_quantity_fn, apply function, and restore shape
+            num_conditions, num_samples = next(iter(estimates.values())).shape[:2]
+            flattened_estimates = keras.tree.map_structure(lambda t: np.reshape(t, (-1, *t.shape[2:])), estimates)
+            flat_tq_estimates = test_quantity_fn(data=flattened_estimates)
+            test_quantities_estimates[key] = np.reshape(flat_tq_estimates, (num_conditions, num_samples, 1))
+
+        # Add custom test quantities to variable keys and names for plotting
+        # keys and names are set to the test_quantities dict keys
+        test_quantities_names = list(test_quantities.keys())
+
+        if variable_keys is None:
+            variable_keys = list(estimates.keys())
+
+        if isinstance(variable_names, list):
+            variable_names = test_quantities_names + variable_names
+
+        variable_keys = test_quantities_names + variable_keys
+        estimates = test_quantities_estimates | estimates
+        targets = test_quantities_targets | targets
+
     plot_data = prepare_plot_data(
         estimates=estimates,
         targets=targets,
diff --git a/bayesflow/utils/dict_utils.py b/bayesflow/utils/dict_utils.py
index 09fa4b853..5d085f0ec 100644
--- a/bayesflow/utils/dict_utils.py
+++ b/bayesflow/utils/dict_utils.py
@@ -282,6 +282,10 @@ def dicts_to_arrays(
         Ground-truth values corresponding to the estimates. Must match the structure and dimensionality
         of `estimates` in terms of first and last axis.
 
+    priors : dict[str, ndarray] or ndarray, optional (default = None)
+        Prior draws. Must match the structure and dimensionality
+        of `estimates` in terms of first and last axis.
+
     dataset_ids : Sequence of integers indexing the datasets to select (default = None).
         By default, use all datasets.
 
diff --git a/bayesflow/utils/plot_utils.py b/bayesflow/utils/plot_utils.py
index aaaca44fe..8de2e4b77 100644
--- a/bayesflow/utils/plot_utils.py
+++ b/bayesflow/utils/plot_utils.py
@@ -23,7 +23,7 @@ def prepare_plot_data(
     figsize: tuple = None,
     stacked: bool = False,
     default_name: str = "v",
-) -> Mapping[str, Any]:
+) -> dict[str, Any]:
     """
     Procedural wrapper that encompasses all preprocessing steps, including shape-checking, parameter name
     generation, layout configuration, figure initialization, and collapsing of axes.
@@ -56,6 +56,12 @@ def prepare_plot_data(
         Whether the plots are stacked horizontally
     default_name      : str, optional (default = "v")
         The default name to use for estimates if None provided
+
+    Returns
+    -------
+    plot_data : dict[str, Any]
+        A dictionary containing all preprocessed data and plotting objects required for visualization,
+        including estimates, targets, variable names, figure, axes, and layout configuration.
     """
 
     plot_data = dicts_to_arrays(
diff --git a/tests/test_diagnostics/test_diagnostics_plots.py b/tests/test_diagnostics/test_diagnostics_plots.py
index f9f29492f..8d4b7883b 100644
--- a/tests/test_diagnostics/test_diagnostics_plots.py
+++ b/tests/test_diagnostics/test_diagnostics_plots.py
@@ -1,4 +1,5 @@
 import bayesflow as bf
+import numpy as np
 import pytest
 
 
@@ -16,6 +17,8 @@ def test_backend():
 
 
 def test_calibration_ecdf(random_estimates, random_targets, var_names):
+    print(random_estimates, random_targets, var_names)
+
     # basic functionality: automatic variable names
     out = bf.diagnostics.plots.calibration_ecdf(random_estimates, random_targets)
     assert len(out.axes) == num_variables(random_estimates)
@@ -46,6 +49,22 @@ def test_calibration_ecdf(random_estimates, random_targets, var_names):
     # cannot infer the variable names from an array so default names are used
     assert out.axes[1].title._text == "v_1"
 
+    # test quantities plots are shown
+    test_quantities = {
+        r"$\beta_1 + \beta_2$": lambda data: np.sum(data["beta"], axis=-1),
+        r"$\beta_1 \cdot \beta_2$": lambda data: np.prod(data["beta"], axis=-1),
+    }
+    out = bf.diagnostics.plots.calibration_ecdf(random_estimates, random_targets, test_quantities=test_quantities)
+    assert len(out.axes) == len(test_quantities) + num_variables(random_estimates)
+    assert out.axes[1].title._text == r"$\beta_1 \cdot \beta_2$"
+    assert out.axes[-1].title._text == r"sigma"
+
+    # test plot titles changed to variable_names in case test quantities exist
+    out = bf.diagnostics.plots.calibration_ecdf(
+        random_estimates, random_targets, test_quantities=test_quantities, variable_names=var_names
+    )
+    assert out.axes[-1].title._text == r"$\sigma$"
+
 
 def test_calibration_histogram(random_estimates, random_targets):
     # basic functionality: automatic variable names