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In obese men visceral adiposity has been associated with obstructive sleep apnea (OSA), while studies in overweight men and women are limited. Our goal was to examine the association between OSA and visceral fat in a relatively non-obese population and assess the effects of a 2month placebo-controlled CPAP use on abdominal fat. 81 subjects, 22 middle-aged men and 20 postmenopausal women with OSA; 19 men and 20 women controls were studied in the sleep laboratory for four nights. Abdominal (visceral-VAT, subcutaneous-SAT) and liver fat were assessed with computed tomography. OSA patients were re-assessed post CPAP and post sham-CPAP. Apneic men had significantly higher VAT than controls, while apneic women had higher SAT than controls. In both genders, OSA was associated with increased liver fat. In men, apnea was associated with VAT whereas in women with subcutaneous, visceral and total fat. CPAP did not affect abdominal and liver fat. In overweight men, visceral adiposity is associated with OSA whereas in women it is global adiposity. In overweight men our therapeutic goal should be the reduction of visceral adiposity and its metaboli