Background: Diabetic retinopathy (DR) with diabetic macular edema (DME) is one of the most common complications of diabetes and can lead to visual loss in young individuals. Purpose: to evaluate the efficacy of posterior subtenon versus intravitreal triamcinolone injection for treatment of diffuse diabetic macular edema. Patients and methods: seventy six eyes of 64 patients having diffuse diabetic macular edema were included and divided into two groups; Intravitreal triamcinolon acetonide group (IVTA group) included 40 eyes of 30 diabetic individuals, injected with 4 mg (0.1ml) IVTA. Posterior subtenon triamcinolon acetonide group (STTA group) consists of 36 eyes of 34 diabetic persons injected with 40 mg (1ml) in the posterior subtenon space. The central subfield macular thickness (CMT) measured with optical coherence tomography (OCT) before injection, 3 and 6 months post-injection was evaluated. Visual acuity as Log MAR, intraocular pressure (IOP) and any complications associated with both techniques ware assessed. Results: the baseline log MAR VA was significantly improved in both groups at one, three, and six months post-injection .The IVTA and STTA groups had significant reduction in CMT three and six months after steroid injection. The mean IOP was 16.6±1.3 mmHg and 15.4±1.1mmHg at the end of follow up in IVTA and STTA groups respectively. Conclusion: both intavitreal and subtenons routes of steroid injection are good alternatives for the treatment of diabetic macular edema, but the intravitreal route has a more pronounced effect while the subtenons route is safer.