Double pituitary adenomas represent up to 2.6 % of pituitary adenomas in large surgical series and up to 3.3 % of patients with Cushing's disease have been found to have double or multiple pituitary adenomas. We report the case of a 60-year-old male patient whose medical history began in 2002 with erectile dysfunction; hyperprolactinemia was found and MRI showed a 6-mm area of delayed enhancement in the lateral portion of the right pituitary lobe. Treatment with cabergoline was started with normalization of prolactin levels; the following MRI, performed in 2005 and 2008, showed shrinkage of the pituitary lesion. In 2005, the patient began to manifest weight gain, hypertension, and facial plethora, but no further evaluations were done. In January 2010, the patient came to our attention and underwent multiple tests that suggested Cushing's disease. A new MRI was negative. Bilateral inferior petrosal sinus sampling showed significant pituitary-to-peripheral ratio and, in May 2010, the patient underwent exploratory pituitary surgery with evidence of a 1-2-mm white-coloured midline area compatible with pituitary adenoma that was surgically removed. Post-operatively, the patient's clinical conditions improved with onset of secondary hypoadrenalism. The histologic examination confirmed a pituitary adenoma (immunostaining was found to be positive for ACTH and negative for prolactin). We report the case of an ACTH-producing microadenoma metachronous to a prolactin secreting microadenoma although not confirmed histologically, shrunk by medical treatment. A review of data in the literature regarding double or multiple pituitary adenomas has also been done.