During ultrasound assessment of a large postinfarct apical left ventricular aneurysm, a related localized area of ventricular wall rupture was discovered by colour flow mapping. Other non-invasive and invasive techniques failed to demonstrate the pseudoaneurysm. The rare combination of a true and false left ventricular aneurysm in one patient and the diagnostic difficulties in this case uniquely illustrate the recent controversy concerning the definition and diagnosis of pseudoaneurysm. The clinical importance of colour flow mapping, as the most sensitive technique in detecting pseudoaneurysm, is emphasized.