Deterioration of pulmonary function can be the sole symptom of early stages of pulmonary complications following allogeneic hematopoietic cells transplantation (alloHCT). The aim of the study was to evaluate the prevalence and types of pulmonary function abnormalities in allogenic cells recipients. Twenty three (5 children and 18 adults) allogeneic hematopoietic cells recipients who underwent pulmonary function assessment before and 6-12 months after alloHCT were included in the study. Forced expiratory volume in 1 s (FEV(1)), forced vital capacity (FVC), total lung capacity (TLC), and lung diffusion capacity for carbon dioxide (D(L)CO) were determined. Values <80% of predicted were considered abnormal. We found significant reductions of FVC, D(L)CO, and TLC after alloHCT. The most important reduction was noted in D(L)CO (pre-alloHCT of 85%±15% vs. post- alloHCT of 60% ± 21%, p< 0.05). Six patients (26%) presented with lung function impairment before alloHCT: obstructive lung disease (4%), restrictive lung disease (13%), and decreased D(L)CO (17%). In 19 patients (83%) pulmonary function abnormalities were demonstrated after alloHCT. The most common disturbance was a D(L)CO decrease that occurred in 16 patients (70%). In conclusion, frequency of pulmonary function abnormalities in patients after alloHCT is high. A diffusion capacity decrease and restrictive pattern of ventilation insufficiency develop in the majority of patients after alloHCT. It would be reasonable to include pulmonary function testing to standard periodic examination in patients qualified for, and after, alloHCT procedure.