Medical students do not sleep enough hours, they should study at night and, therefore, they have excessive daytime somnolence that could produce attention disorders affecting their academic performance. The objective was to determine the prevalence of excessive daytime somnolence and prevalence of poor quality in students of a private university in Ecuador, and the relation existing between these disorders and their academic performance. A cross-sectional study that included 219 undergraduate medical students, 57.5% of them, female. Spanish paper-based Epworth Somnolence Scale and the Pittsburgh Sleep Quality Index were applied. Sociodemographic variables were also measured. Statistical methods were performed to make comparisons between groups (comparison of proportions and means) and bivariate and multivariate regression logistic were performed to assess the association between academic performance and sleep quality after adjusting for other covariates. Excessive daytime somnolence occurred in 42.0% (95%CI 35-49) of students, slightly higher in women and 83.1% reported bad quality of sleep according to the Pittsburgh scale. It was found that 40.6% had a poor academic performance being alcohol consumption a risk factor for it. There was no statistical association between excessive daytime somnolence, poor sleep quality, and academic performance. Excessive daytime somnolence and bad quality of sleep are very common among medical students, but this disturbed sleep pattern seems no to be associated with poor academic performance.