Background: Panretinal photocoagulation (PRP) is considered the gold standard for first line therapy in proliferative diabetic retinopathy (PDR). The aim of PRP is to prevent visual loss following vitreous hemorrhage, tractional retinal detachment, and neovascular glaucoma, by leading to regression of neovascularization. Objective: The purpose of this study was to compare the effect of diabetes duration on proliferative disease regression after pan-retinal photocoagulation using a conventional green laser versus a multispot pattern scan laser. Subjects and Methods: Eighty eyes with newly diagnosed proliferative diabetic retinopathy were randomly divided in to two groups each composed of 40 eyes: group (A) in which patients were received standard argon laser panretinal photocoagulation and group (B) in which patients were received pattern scan multispot panretinal photocoagulation. Changes in central macular thickness and BCVA at 1st, 4th, 12th week and 6th month follow-up were compared to baseline measurements. Fundus fluorescein angiography was performed at 4 weeks, 12 weeks and 6 months to assess regression of PDR. Results: by the end of the study, complete regression occurred in 37 (92.5%) of patients in conventional laser group and 36 (90%) patients in PASCAL group, while persistence of the disease occurred in 3 (7.5%) patients in each group and recurrence occurred 1 (2.5%) in PASCAL group. There was no statistically significant correlation in each study group between clinical outcome and age or duration of DM. Conclusion: There was no statistically significant correlation in each study group between duration of DM and proliferative disease regression.