The high demand for full polysomnography and the better quality of sleep at home are the main reasons for performing home sleep studies. Home respiratory monitoring has been evaluated in several studies, but the influence of setting on the results of unattended respiratory monitoring has not been assessed to date. Unattended monitoring of respiratory variables at home and in the sleep laboratory was conducted in 35 consecutive patients with suspected sleep apnoea/hypopnoea syndrome. Respiratory variables during sleep, rate of successful studies and patient preference were compared. The data acquisition failure rate was 2.8% in the sleep laboratory and 5.7% at home. The mean difference between apnoea/hypopnoea indices (AHI) obtained from home and laboratory studies was -0.21 +/- 8 (95% confidence interval 3.27-2.84). Using the method comparison approach of Bland and Altman, the limits of agreement of the mean difference between AHI home and AHI laboratory were -16.7 and 17.1. No difference was observed between the studies in time spent in different body positions. When patients were asked where they would prefer to repeat the sleep study, 53% replied at home, 28% in hospital and 19% showed no preference. It was concluded that the setting of unattended respiratory monitoring (home or sleep laboratory) influences neither the number of valid studies nor the results of the respiratory parameters measured; most patients, however, preferred home studies.