BACKGROUND: Knowledge of hatha yogic exercises, the most used yoga style, for increasing functional capacity in patients with obstructive pulmonary diseases remains limited. AIM: The aim was to evaluate the effects and feasibility of hatha yoga (HY) compared to a conventional training program (CTP) on functional capacity, lung function and quality of life in patients with obstructive pulmonary diseases. DESIGN: Randomized clinical trial. SETTING: The study was performed at the Karolinska University Hospital, Stockholm, among outpatients. POPULATION: Thirty-six patients with obstructive pulmonary disease. METHODS: Forty patients were randomized with 36 (24 women, median age =64, age range: 40-84 years) participating in HY (N.=19) or CTP (N.=17). Both HY and CTP involved a 12-week program with a 6-month follow-up. Functional capacity (using the 6-Minute Walk Test), lung function (spirometry), respiratory muscle strength (respiratory pressure meter), oxygen saturation (SpO2), breathlessness (Borg), respiratory rate (f) and disease-specific quality of life (CRQ) were measured at baseline, at 12 weeks and at a 6-month follow-up. RESULTS: Testing for interactions (group x time) with ANOVAs showed significant effects on the CRQ fatigue (P=0.04) and emotional (P=0.02) domains, with improvements in the CTP group after the 12-week intervention (P=0.02 and 0.01, respectively) but not in the HY group. No between group effects emerged, however, within each group, significant improvements emerged for the six-minute walk distance (6MWD) after 12-week intervention (HY: mean difference 32.6 m; CI: 10.1-55.1, P=0.014; CTP: mean difference 42.4 m; CI: 17.9-67.0, P=0.006). Secondary outcomes: within-group improvements in CRQ appeared in both groups. Within the HY group, f decreased and SpO2 increased. Improved effects after follow-up emerged only for the CTP group for diastolic blood pressure (P=0.05) and CRQ emotional and fatigue domain (P=0.01). CONCLUSIONS: There were no between-group differences. After 12 weeks, 6MWD improved significantly within both groups. Within the HY group, improvements in the CRQ mastery domain, f and SpO2 emerged. Within the CTP group, there were improvements in lung function parameter forced vital capacity, respiratory muscle strength and all CRQ-domains. The CTP also exhibited effects on CRQ after the 6months follow-up. CLINICAL REHABILITATION IMPACT: Limited effects of HY and CTP emerged. HY seems feasible and safe as a form of physical exercise for pulmonary disease patients. As part of the rehabilitation, HY may constitute an alternative to other physical training activities and may be a useful addition to formal rehabilitation programs.