Purpose. We assessed the exercise tolerance and cardiorespiratory responses during 2‐month weight‐loss programmes using the 6‐minute walking test (6MWT) in obese children. Methods. Twenty‐eight male obese children were randomly assigned to either a control group (C), an energy restriction group (R), an exercise training at maximum lipid‐oxidation (LIPOXmax) group (E), or an energy restriction/training group (RE). The body composition, the submaximal incremental cycling exercise, and the 6MWT were performed before and after the 2‐month programme. Results. After the programme, RE group showed a significant improvement of body composition (body weight reduced by 6.3 ± 1.5 kg, p < 0.01), and an increase of 6‐minute walking distance (6MWD) (+13.7%, p < 0.01). Similarly, maximum oxygen uptake calculated according to the American College of Science Medicine guideline (VO2maxACSM) and VO2max predicted from 6MWD were respectively higher (+12.9% and +10.0%, p < 0.01) than the R or E groups. Bland‐Altman analysis highlighted an agreement of these two methods of VO2max measurement. Moreover, in all participants the 6MWD was significantly correlated with VO2maxACSM and LIPOXmax (r = 0.77, p < 0.001 and r = 0.67, p < 0.01; respectively) before the programme as well as their changes in percentage over the programme (r = 0.85 and r = 0.86, p < 0.0001; respectively). Conclusions. We concluded that a 2‐month weight‐loss programme including energy restriction and exercise training targeted at LIPOXmax improved body composition and cardiorespiratory tolerance in obese children. Furthermore, the 6MWT could be considered as a useful and reliable tool for the assessment and the follow‐up of cardiorespiratory responses during weight‐loss programme in obese children. Copyright © 2010 John Wiley & Sons, Ltd.