Continuous positive airway pressure (CPAP) is the first-line therapy for obstructive sleep apnoea (OSA). Residual apnoea and/or hypopnoea events, that is an apnoea-hypopnoea index (AHI) > 5, during CPAP contribute to treatment drop-out. The clinical scenarios triggering residual events during CPAP use are poorly described. Underlying co-morbidities, especially cardiovascular diseases, lifestyle factors, OSA characteristics at diagnosis and type of mask have been suggested as potential contributors.Patients from the prospective French sleep apnoea registry diagnosed with OSA (AHI ≥ 15 events/h) treated with CPAP were included. Logistic regression analysis identified factors associated with a risk of residual AHI > 5 events/h on CPAP.The 12 285 OSA patients were predominantly men (n = 8715, 70.9%), middle-aged (58.2 (49.8; 66.1) years) and obese (median body mass index: 31.3 (27.7; 35.6) kg/m ). Most had an AHI ≤ 5 events/h (n = 9573, 77.9%) versus 22.1% with AHI > 5/h. The latter were less CPAP adherent (5.75 (4.01; 7.00) vs 6.00 (4.53; 7.00) h/night). In multivariable analysis, factors associated with residual AHI >5/h were male sex, age, sedentary lifestyle, OSA severity, cardiovascular co-morbidities (heart failure and arrhythmia) and type of interface (orofacial mask versus nasal mask: OR = 2.15 (95%CI: 1.95; 2.37)). A subgroup analysis found that patients using pressures above 10 cm H O were 1.43 (95% CI: 1.3; 1.57) times more likely to have residual AHI > 5/h.Knowing about risk factors for residual apnoeic-hypopnoeic events may assist in the timely provision of personalized care including the type of PAP therapy, attention to co-morbidities and choice of interface.