T2-weighted sequences are an integral part of magnetic resonance (MR) imaging performed for the characterization of adnexal lesions. A relatively small number of these lesions demonstrate low signal intensity on T2-weighted MR images. In the majority of cases, a specific diagnosis can be made by interpreting the signal intensity of the lesion with respect to certain pathologic correlates, including blood products, smooth muscle, fibrous tissue, and calcification, as well as high lesion cellularity. For example, lesions that are at least as dark as skeletal muscle are almost always benign, whereas those whose T2 signal intensity is higher than that of skeletal muscle constitute a more heterogeneous group composed of benign, borderline, and malignant disease entities. The authors propose a diagnostic algorithm that takes these features into account, as well as the appearances of the lesion with additional pulse sequences, to aid in the correct interpretation of T2-hypointense adnexal lesions. Knowledge of the anatomy, the T1-weighted imaging features, and the enhancement characteristics of adnexal lesions allows accurate characterization of these lesions, resulting in appropriate patient management.