Summary We prospectively observed 36 haematological patients with mucormycosis from nine hospitals of St. Petersburg during 2004–2013. The most frequent underlying diseases were acute leukaemia (64%), and main risk factors were prolonged neutropenia (92%) and lymphocytopenia (86%). In 50% of the patients, mucormycosis was diagnosed 1–65 days after invasive aspergillosis. Main clinical form of mucormycosis was pulmonary (64%), while two or more organ involvement was noted in 50% of the cases. The most frequent aetiological agents of mucormycosis were Rhizopus spp. (48%). Twelve‐week survival rate was 50%. Combination therapy (echinocandins + amphotericin B forms) and recovery from the underlying disease significantly improved the survival rate.