Gynaecomastia is uni- or bilateral breast enlargement in males associated with benign hyperplasia of the glandular, fibrous and adipose tissue resulting from oestrogen-androgen imbalance. Asymptomatic gynaecomastia is a common finding in healthy male adults and does not have to be treated, while symptomatic gynaecomastia might be the symptoma of many pathological conditions and requires meticulous diagnosis and therapeutic management. The commonest causes of gynaecomastia in the Polish population include liver cirrhosis and drugs used to treat its complications. The current study presents the case of severe painless gynaecomastia in a patient with decompensated alcoholic liver cirrhosis, treated with spironolactone because of ascites. Breast enlargement assessed a IIb according to the Simon’s Scale or III according to the Cordova-Moschella classification, developed slowly over the two-year period of low-dose spironolactone therapy The course and dynamics of disease are described and the main mechanisms leading to its development discussed. The importance of effective treatment of patients with severe gynecomastia is emphasized as the disease may result in significant psychosocial problems.