Purpose: Due to the possible interplay of factors predisposing to severe COVID-19 outcomes and negative health consequences of poorly controlled OSA, adherence to continuous positive airway pressure (CPAP) therapy among OSA patients might be crucial during COVID-19 pandemics. Lockdown-related changes in CPAP adherence were investigated in CPAP users willing to participate in this study. Pre-lockdown adherence, age, gender, comorbidities and anxiety were analyzed as predictors of COVID-19 lockdown adherence. Patients and Methods: A cross-sectional study performed at Split Sleep Medicine Center included 101 severe OSA patients (78.2% male). CPAP memory cards were assessed during 6 months of pre-lockdown and 40 days of lockdown (March/April 2020) period. A total of 81 patients in pre-lockdown met good CPAP adherence criteria (>/=4 hours/night on 70% nights). Results: CPAP adherence improved during COVID-19 lockdown in the total sample of severe OSA patients. The percentage of adherent nights and CPAP usage hours per night increased during lockdown in good pre-lockdown CPAP adherers (p=0.011 and p=0.001, respectively), women (p=0.003 and p=0.001, respectively) and respondents younger than 58 years (p=0.007 and p<0.001, respectively). Out of 20/101 poor pre-lockdown CPAP adherers, 9 have shifted to good lockdown adherence. When comorbidities, BMI and anxiety were taken into account, older and male respondents were recognized as less likely to improve CPAP usage hours during lockdown (R(2)=9.4%; p=0.032). Conclusion: The lockdown-related CPAP adherence improved in severe OSA patients, with a shift in almost half of poor pre-lockdown adherers towards good lockdown CPAP adherence. Women, younger and good pre-lockdown CPAP adherers were more adherent during lockdown. Despite being vulnerable groups for both OSA and COVID-19, no expected adherence improvements were observed in men and older patients.