Notable regional and seasonal variation has been reported in the rate of hospital admissions for chronic obstructive pulmonary disease (COPE). The aim of this study was to assess the variation in the length of hospital stay for COPD in Finland on the north south axis and by season. For this purpose, the patient records of subjects aged over 45 hospitalised altogether 153,401 times with COPD as their primary diagnosis during 1987 - 1998 were retrieved from the Finnish Hospital Discharge Register maintained by the National Research and Development Centre for Welfare and Health. During this period, the average length of hospital episodes was 9.8 (SD) 47.8) days in northern Finland and 11.9 (SD 54.5) days in southern Finland (p = 0.001). Throughout Finland, the mean duration of hospital stay was longest in the winter, 12.3 (SD) 62.3) days, and shortest in the summer, 11.0 (SD) 42.3) days (p = 0.001). The mean duration of hospital stay in northern Finland was also longest in the winter, 10.6 (SD 56.7) days, and shortest in the summer, 8.8. (SD) 26.7) days (p = 0.015). Hospital episodes for COPD vary in duration in Finland, probably mainly due to regional differences in health care resources and treatment routines. The light and warm northern summer may also speculatively serve to shorten hospital episodes.