Background: Spinal anesthesia is a gold standard procedure in urologic, orthopedic, obstetric and gynecological operations. However, post dural puncture headache (PDPH) is very annoying, there is no effective preventive or treatment method for it. Aim of work: This study compared the effect of IV dexamethasone versus intrathecal dexamethasone as adjuvant to bupivacaine, on prevention of PDPH.Methods: A comparative, double blind, randomized prospective study was conducted on 630 patients, ASA physical status I and II, of both sexes, undergoing lower abdominal and lower limb surgeries under spinal anesthesia. Patients were randomly divided into 3 equal groups. Group 1: received bupivacaine 0.5% 3 ml and 1 ml normal saline intrathecal and 8 mg intravenous dexamethasone in 10 ml saline. Group 2: received bupivacaine 0.5% 3 ml and 4 mg (1 ml) dexamethazone intrathecal, and 10 ml normal saline intravenous. Group 3: received bupivacaine 0.5% 3ml and 1 ml normal saline intrathecal, and 10 ml normal saline intravenous. Results:In Group 1, PDPH occurred in 13 patients (6.19%) in post anesthesia care unit (PACU) and in 20 patients (9.5%) within 48 hours. In group 2, PDPH occurred in 14 patients (6.6%) in PACU and 22 patients (10.4%) had PDPH within 48 hours. In group 3, 16 patients (7.6%) had PDPH in PACU and within 48 hours 21(10%) had PDPH. There was no statistically significant difference between the three groups. Conclusion:Incidence of post dural puncture headache, between using intrathecal bupivacaine alone or combined with intrathecal dexamethasone (4 mg) or intravenous dexamethas-one (8 mg) was similar.