Background: Spasticity affects a large number of children, mainly in the setting of cerebral palsy, however, only a few paediatric neurosurgeons deal with this problem. This is mainly due to the fact that until 1979, when Fasano has published the first series of selective dorsal rhizotomy (SDR), neurosurgeons were able to provide such children only a modest help. Objectives: This work aims to study the effect of performing selective dorsal rhizotomy operation on patients suffering from spastic diparesis due to cerebral palsy, and the aim of surgery is to relieve the present spasticity, which is predominantly seen in the lower limbs, and to improve motor function. Patients and methods: This study was done on 30 patients with ages (4-12) years old, with mean age 8 years old, included patients from both sexes (16 males, 14 females), on Al-Azhar University Hospital and Dar El-shefa Hospital, in the period from January 2019 to August 2020. Results: In our study, we achieved significant results in our patients with sectioning 30-60% of rootlets, with preservation of motor power and no sensory loss. According to our results, an important factor that may improve outcome and prognosis of patients is the pre-operative mental state, as patients with acceptable mental ability has the potential to participate in more active physiotherapy programs that improve outcome greatly. However, even with decreased mentality there is post-operative decrease in muscle tone and reflexes, which may aid in making patient's decubitus less prone to pressure sores, and make the patient easier to handle, so, the proper care can be achieved. Also according to our study, the higher the grade of Aschworth's score is a good prognostic factor of achieving faster improvement of spasticity and gait. Conclusion: selective dorsal rhizotomy is not a cure for cerebral palsy. The procedure offers spastic CP children improved motor capabilities and increased levels of functioning. Achieving maximal benefits depends on how much and which of the posterior rootlets are cut.