Aim: The purpose of this randomized spilt mouth clinical trial was designed to compare the effectiveness of non-surgical periodontal therapy through plaque control, scaling and root planing with the surgical one using Modified Widman’s flap, in reduction of periodontal pockets 5 - 8 mm in depth. Material and Methods: Seventeen patients males and females with advanced periodontal diseases who were recruited. Full mouth scaling, polishing and root planning applied to all patients followed by oral hygiene instructions. One month later, Modified Widman’s flap procedure applied to one sextant which was randomly selected. Periodontal parameters measurements were taken again at days 1 month, 3 month and 6 months. Results: For both surgical and non-surgical treated sites, the Mean and Standard deviations of periodontal Parameters, Plaque index (PI), Gingival index (GI), Probable pocket Depth (PPD) and Gingival recession showed significant reduction. Conclusion: Both Surgical therapy using Modified Widman’s Flap and Non-surgical treatment by scaling and root planing are equally effective in the reduction of periodontal pockets (5 - 8 mm) depth.