To investigate the cross-sectional associations of daytime sleepiness with coronary plaque volume and composition in patients with obstructive sleep apnea (OSA), and whether or not these associations are modified by age, gender, and obesity.Patients who were confirmed with OSA through respiratory polygraphy and also underwent coronary CTA at a tertiary hospital were consecutively enrolled. The interval between the sleep monitoring and coronary CTA scan was  < 3 months. Every patient completed the Epworth sleepiness scale (ESS) to assess daytime sleepiness, and an ESS score of ≥ 11 was recognized as excessive daytime sleepiness (EDS). Coronary plaque volume and composition were measured using semi-automatic software.Of the 394 patients with OSA (median [IQR] age, 56.0 [49.0-64.0] years; median [IQR] body mass index, 27.9 [25.5-30.2] kg/m2; median [IQR] apnea-hypopnea index, 21.3 [11.7, 36.3] events/h), a total of 200 patients had EDS. In the overall participants, a significant dose-response relationship between ESS scores and low-attenuation plaque volume was found in the fully adjusted model (P = 0.019). Further analysis demonstrated that there was a significant interactive effect of ESS levels and obesity on coronary plaque volume (all P values for interaction analysis < 0.05). Specifically, ESS levels were associated with total plaque volume, volumes of noncalcified, low-attenuation, and calcified plaque (P = 0.008, 0.006, 0.005, and 0.043 respectively) in obese patients with OSA.Daytime sleepiness is significantly correlated with increased coronary plaque burden among patients with OSA. Thus, clinicians should recognize that patients with OSA reporting high ESS scores, especially those with obesity, are more prone to experience adverse coronary events.© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.