Three-dimensional (3D) modelling and printing greatly supports advances in individualized medicine and surgery. In congenital cardiac surgery, 3D-models and printed prototypes offer advantages of better understanding of complex anatomy, hands-on preoperative surgical planning and emulation, improved communication within the multidisciplinary team and to patients. 3D-virtual and printed models often add important new anatomical findings and prompt alternative operative scenarios. Validity and realisation of possible clinical benefits were studied. Computed tomography-angiography raw-data were segmented into 3D-virtual models of the heart-great vessels. Prototypes were 3D-printed as real-size "blood-volume" (rigid material), and 1.5×-scaled "hollow" (translucent, flexible material). Accuracy of the models was evaluated intraoperatively. We produced 3D-prototypes of the heart-great vessels for 12 case-scenarios (6 males, median age: 11 months) undergoing complex intracardiac repairs. Accuracy was excellent in millimeter-range. Representation of the atrioventricular valves is currently unsatisfactory. Models refined diagnostics in 8/12 and provided new anatomic information in 6/12 cases (e.g., aberrant coronary origin/course, newly-discovered intracardiac communication, etc.); in 10/12 cases they contributed to an improved operative plan (surgical approach, modification of intracardiac repair, etc.); an alternative operative plan emerged in 6/12 cases. Complex operative procedures (staged reoperations in 10/12; Aristotle-score median: 11; 10-14) emulated on 3D-models were materialized successfully. No morbidity/mortality occurred. Acceptance-index of the 3D-models was maximal among the multidisciplinary clinical team and patients/relatives. 3D-printed models can contribute to the safety of complex congenital cardiac surgeries in selected scenarios. Besides their numerous benefits, currently inadequate financial coverage of the extra time/labour and material/machinery by insurance is mentioned as a major drawback. Orv Hetil. 2019; 160(19): 747-755.