Abstract Background: Dynamic contrast-enhanced MRI is highly sensitive in the detection of breast malignancy; however, its value is limited in cases of non-mass enhancement. Diffusion-weighted imaging (DWI) might be of great benefit in the diagnosis of non-mass breast lesions. Aim of Study: The aim of this study is to determine the value of diffusion-weighted MR imaging in the evaluation of indeterminate non-mass breast lesions, obviating the need for biopsy. Patients and Methods: Thirty-three female patients be-tween the ages of 3 8-56 years (mean age, 45 years) with non-mass lesions on breast MRI were included in this study. The lowest ADC value for each lesion was recorded. Core-needle biopsies were performed after attaining patients' consent. Results: This study included 33 non-mass breast lesions noted on breast MRI. The size of the lesions ranged from 0.2 to 1.4cm (mean size, 0.6cm). The morphological characteristics of the lesions and their signal intensity curves on dynamic contrast-enhanced MRI were recorded. A threshold ADC value of 1.03x10-3 mm2/s was set for discrimination between benign and malignant lesions. The range of ADC values was 1.3 x 10-3 mm2/s to 2.6 x 10-3 mm2/s. Conclusion: Diffusion-weighted imaging is effective in the evaluation of indeterminate non-mass breast lesions on breast MRI and can be used as an alternative to biopsy.