Non-compaction of the ventricular myocardium is an anomaly of myocardial morphogenesis that leads to persistence of the embryonic myocardium with an excessively prominent trabecular meshwork and deep intertrabecular recesses. This report describes 3 cases of isolated left ventricular non-compaction in adults leading to terminal heart failure. We describe their distinctive myocardial histopathology and prospective diagnosis by cardiac magnetic resonance imaging (CMR). Heart transplantation was the only treatment option for all 3 of these severely ill patients. Isolated ventricular non-compaction should be considered in patients with severe idiopathic cardiomyopathy whose symptoms appear in early adulthood, and consideration given for early transplantation. Non-invasive imaging with CMR can confirm the diagnosis.