Two-dimensional (2-D) ultrasound (US) of rotator cuff lesions is a well-established tool. The aim of this study was to elucidate if the use of 3-D sonography can increase the diagnostic yield of US. A total of 40 patients were preoperatively evaluated using 2-D and 3-D sonography, and these results were compared to intraoperative findings. Ultrasound was performed on a 530D US machine (Kretztechnik, Zipf, Austria) with a 10-MHz transducer. We found an increased validity of 3-D imaging, mainly based on the higher reliability in the diagnosis of partial-thickness cuff lesions. Sensitivity and specificity were found to be 91% and 82% for 3-D sonography and 74% and 82% for 2-D sonography, respectively. With 3-D US partial-tear rotator cuff lesions can be predicted more accurately.