The association of obstructive sleep apnoea (OSA) and chronic obstructive pulmonary disease (COPD) is not rare as COPD and OSA are both frequent diseases. The aim of this study was to determine the effect of OSA on quality of life (QOL) in patients with overlap syndrome (OVS). Thirty subjects with OVS and 15 control subjects participated. The St George's Respiratory Questionnaire (SGRQ) was used to determine QOL. The control group included subjects with COPD and no evidence of OSA by overnight polysomnography. All subjects were habitual snorers with normal Epworth Sleepiness Scale scores. Significant differences were found between the groups for the total score and each of the three components of the SGRQ suggesting worse QOL in OVS patients (symptoms 54.9 +/- 18.9 vs. 38.2 +/- 19.3, p = 0.008; activity 59.2 +/- 16.2 vs. 44.4 +/- 11.3, p = 0.003; impacts 35.2 +/- 23 vs. 20.8 +/- 8.7, p = 0.025 and total 45.7 +/- 17.7 vs. 30.9 +/- 8.7, p = 0.004 in OVS patients and control group, respectively). Obstructive sleep apnoea has a major impact on QOL in patients with OVS and can exist in COPD patients with habitual snoring even in the absence of daytime sleepiness. Further studies are needed to determine the impact of OSA treatment on QOL and morbidity in this population.