For the diagnosis of supra-renal tumours or tumours of supra-renal rests, it is necessary to employ all available radiological methods as well as the clinical data. Two cases are described in which a supra-renal tumour had been "masked" and found at operation. In the first case a cyst in the tail of the pancreas had been considered, in the second, a tumour of the renal hilum or ureter had been diagnosed. It is concluded that in the differential diagnosis of a cyst of the tail of the pancreas, supra-renal tumours must be included. Further, vascular lesions in the vicinity of the kidney associated with normal renal vasculature may be due to tumours of supra-renal origin.