The data of clinical, macro- and micrometric, histological, and immunohistochemical studies of the heart were analyzed in patients with left ventricular noncompaction (LVNC). Materials from 7 patients: 5 hearts of recipients after heart transplantation, one heart of a dead patient, and one endomyocardial biopsy specimen were investigated. The investigations showed that this disease was accompanied by a preponderance of a noncompact layer with its ratio to a compact layer (2.4:6.6) in the left ventricle and by myocardial hypertrophy and fibrosis in all cases, by endocardial fibroelastosis and discomplexation of muscle fibers by more than 15% of the specimen area in 6 of the 7 cases, by right ventricular hypertrabeculation and myocarditis in 5 cases, and by lipomatosis and impaired connexin 43 expression in 4 cases. Only one of the four patients was found to have MYH 7 gene mutation. The results of MRI of the extracted heart coincided with morphological findings in 100% of cases. The comparative study demonstrated that this disease had simultaneously morphological features of both LVNC and restrictive, hypertrophic, dilated cardiomyopathy. The findings may suggest that the LVNC phenotype may be formed under the influence of various modifying factors (hemodynamic and inflammatory ones).