Context: Computed tomography (CT) unenhanced attenuation value of !10 Hounsfield units (HU) has an excellent specificity (98%) to diagnose lipid-rich adrenocortical adenomas (ACAs) with a weaker sensitivity (71%). Objective: To determine from a routine clinical perspective if unenhanced attenuation value is influenced by cortisol secretion in ACAs. Design: This was a retrospective study of cases collected between 2009 and 2012. Setting: This study was conducted in a tertiary-care university hospital. Patients: Seventy-two patients operated on for an ACA (Weiss score %2) were analysed. Thirty-four patients had an ACA oversecreting cortisol (Cush-ACA). Thirty-eight patients had an ACA without cortisol oversecretion (Non Hyper-ACA). Main outcome measure: CT unenhanced attenuation value was correlated with the functional status. The Weiss score items were analysed. Results: Among the 34 patients with a Cush-ACA a minority (nZ7) had an unenhanced attenuation value under 10 HU. Among the high precontrast density (O10 HU) Cush-ACAs, washout analysis after contrast administration was consistent with the benign nature of the tumor in w60% of the cases. Less than 25% clear cells (lipid-rich cells), a Weiss score item, was present in 50% of the Cush-ACAs in favour of a lipid-poor content. Conclusions: Unenhanced attenuation value has a poor sensitivity to diagnose an ACA in case of cortisol oversecretion due to poor lipid content. Nevertheless, the accuracy of washout analysis was preserved in the group of Cush-ACAs.