Background: orbital lesions represent a spectrum of benign and malignant lesions in adults and children that can be challenging to diagnose and treat. Imaging plays an important role in diagnosis, due to a potentially limited clinical examination and risks associated with biopsy. Magnetic resonance imaging (MRI) is a powerful tool for imaging the orbit, due to the excellent tissue contrast it provides. Aim: this study aims at assessing the ability of diffusion weighted magnetic resonance imaging to differentiate the benign from malignant orbital lesions. Patients and Methodology: this study population included 25 patients; they were attended El-Demerdash University Hospital with non-traumatic orbital lesions. All patients had fulfilled specific inclusion and exclusion criteria. The patients were evaluated by MRI orbit and diffusion study in attempt to differentiate the benign orbital lesions from malignant one. Results: the pool of our study is 25 patients (16 female and 9 males) with orbital lesions, the patients age ranged from 1 year to 70 years. There are 48% of the cases diagnosed as having benign lesions and 52% have malignant lesions.Retinoblastoma is the commonest (12%) pathological diagnosis.The calculated apparent diffusion coefficient (ADC) values of the lesions ranged from 0.6 – 2.1 x 10^-3 mm²/sec. The ADC value of 0.89 x10^-3 mm²/sec is a cut off between benign and malignant orbital masses. Conclusion: we concluded that the combination of conventional MRI finding and ADC calculation together with clinical finding could improve the diagnostic efficacy of MRI in the differentiation between benign and malignant orbital masses with considering the cut off ADC value between benign and malignant orbital masses.