Soinio et al. recently compared the diagnostic accuracy of 11C-metomidate PET (11C-MTO-PET) and cosyntropin-stimulated adrenal venous sampling (AVS) for the subtyping of patients with primary aldosteronism (PA), who were diagnosed according to the 2008 Endocrine Society guidelines. They concluded that 11C-MTO-PET offered no diagnostic usefulness in subtyping of PA patients. In our view, this conclusion needs to be taken with great caution owing to a number of concerns that can be raised concerning their study