MR imaging is useful in differentiating and characterizing renal masses. A careful evaluation of the signal characteristics and morphology of a renal mass combined with the ancillary imaging findings and patient history should assist the radiologist in making the proper diagnosis or recommending the appropriate treatment in most cases. This pictorial essay demonstrates the typical MR imaging features of common renal masses including renal cell carcinoma (RCC), oncocytoma, angiomyolipoma, metastases, transitional cell carcinoma (TCC), lymphoma, and arteriovenous malformation (AVM), and highlights several potential diagnostic pitfalls in making the proper diagnosis.