Introduction: Obstructive sleep apnoea (OSA) may be observed in as much as 22% of men and 17% of women. It affects the structural organisation of sleep and may lead to numerous negative consequences. Aim of the study: Assessment of the intensity of sleepiness during the day and its influence on selected aspects of daily functioning of patients suffering from OSA. Material and methods: The study was carried out in a group of 49 patients whose average age was 55.27 ±12.80 years. The diagnostic survey method was used with the application of a self-designed questionnaire, Epworth Sleepiness Scale (ESS) and WHOQOL-BREF scale. Results: The average ESS score obtained by the respondents was 10.11 ±5.60. The incidence of mild excessive daytime sleepiness was observed in 42.86% of patients, whereas 16.33% of respondents suffered from severe excessive daytime sleepiness. The most frequent problem reported by respondents was daytime fatigue, which was observed in 87.76% of cases. The general quality of life (QoL) was relatively high (4.96 ±0.78). The environment domain was rated the highest (15.42 ±1.89), and psychological-the lowest (12.68 ±2.53). Conclusions: A significant correlation was found between respondents' age and the intensity of daytime sleepiness. Higher ESS scores were observed in patients who experienced sleepiness and fatigue after a full night of sleep, had difficulties fulfilling their household chores due to tiredness and/or sleep deprivation, or suffered from memory and/or concentration problems. No correlation was observed between the intensity of perceived daytime sleepiness and the QoL.