Objectives: To assess the effect of variable time and power of Low- level Diode Laser Irradiation therapy (LLLT) in Management of Myofascial Pain Dysfunction syndrome with different wavelength and duration. Patients and Methods:The study was performed onforty-eight adult patients suffering from pain related to the joint area and or limited mouth opening: diagnosed as a myofascial pain dysfunction candidate. Patients were randomly divided into two equal groups; each group contained 24 patients. Group I:t:ed by using diode laser dose: of 940 wave-length dose, 1w power. Patients were randomly divided into two subgroups: twelve patients on each, according to the time of application. Subgroup A: session is 60 seconds. Subgroup B: session is 30 seconds. Group II They were treated by using a laser dose of 940 wave-length diode laser with a power of 1.5 w.Patients were randomly divided into two subgroups: twelve patients on each. Subgroup A: 60 seconds session. Subgroup B: 30 seconds session.In both groups, each patient received 3 sessions per week for 4 weeks. The laser is applied on superficial part of the masseter muscle, the anterior bundle of the temporalis muscle and the buccal vestibule opposite to the upper second and third molar to reach the lateral pterygoid muscle. Pre andPostoperative evaluation were performed using:Helkimo, index, VAS, Algometer, Maximum mouth opening, EMG. Followup were carried out at 1month, 3month and 6month. Result: statistically significant improvement group was present in group II subgroup B statistically significant higher mean differences in MMO, Algometric pressure, Electromyography during all follow-up intervals. Conclusion: therapeutic use of LLLT is beneficial for pain relief and enhance mouth opening in case of MPD. This can serve as an adjunct method in treatment MPD.