Study aim: To assess the suitability of the short 7-day IPAQ (self-completed) adapted to Polish population. Material and methods: Two surveys were conducted in 2005 on 296 random subjects (aged 20-60 years) from Warsaw and the Mazowiecki region. From these, 54 men and 79 women were requested to fill questionnaires, and 70 men and 93 women, were interviewed by an experienced interviewer using the same questionnaire. Polish version of IPAQ, approved by the IPAQ study group was used. Results: A high level of physical activity (at least 1500 Met[middle dot]min/wk in total) was declared significantly (p less than 0.001) more frequently by subjects who filled themselves the questionnaires than by those interviewed. In particular, the declared time spent on vigorous exercises seemed overestimated by the former category of subjects (p less than 0.05). In case of moderate exercises the situation was reversed, and the frequency of reporting them was higher in the interviewed category than in the other one (p less than 0.05), irrespectively of gender or education. Total activity ranged from 99 to 44000 (!) Met[middle dot]min/wk (median value 1386 Met[middle dot]min/wk) in the self-completing category and from 99 to 5544 Met[middle dot]min/wk (median value 320 Met[middle dot]min/wk) in the interviewed group. Conclusions: The technique of self- completing questionnaires ought to be applied with care, as the example of Poland showed it may overestimate the physical activity expressed in MET[middle dot]min/week. (Contains 4 tables and 1 figure.)