Sleep is one of the most important factors contributing to health. Although same studies examining the relationship between sleep duration and mortality, has not been fully discussed. We consecutively studied two hundred and fifty Caucasian subjects, normoweight, who were referred for ambulatory blood pressure monitoring (APM). Quality of sleep was evaluated through the Pittsburgh Sleep Quality Index (PSQI). PSQI assessed subjective sleep quality of the past 4 weeks and was administered during the personal interview. A global PSQI > or =5 has a diagnostic sensitivity of 89.6 and specificity of 86.5 in distinguishing "poor sleepers"(PSQI > or =5) from "good sleepers" (PSQI <5) subjects. Hypertension, type 2 diabetes mellitus and sleep's quality disorders were reported respectively in 53.4%, 12.5% and 35.2% of the total population examined. The prevalence of hypertension was 87.1% in "poor sleepers" subjects versus 35.1% in "good sleepers" subjects (p<0.0001). Our results permit to conclude that, as the sleep-disordered breathing, also the sleep's quality disorders, evaluated by PSQI, are associated with significant comorbidities, as hypertension and diabetes mellitus. We hypothesize that the valuation of the quality of sleep through the Pittsburgh Sleep Quality Index (PSQI) could be considered in screening for cardiovascular risk.