To see accuracy of ultrasound scan to detect patent processus vaginalis in padiatric patient. We investigated the presence of contralateral patent processus vaginalis (CPPV) by Ultrasound scan (US) in children with clinically diagnosed unilateral inguinal hernia. Thirty patents (17 boys and 13 Girls) with unilateral inguinal hernia underwent US examination using a 7.5 MHZ transducer. If a CPPV was visible as a hydrocele (inflow of peritoneal fluid) in to a processus vaginalis on straining, then US scanning was performed while the patient was at rest and while inducing straining by standing, coughing and or crying. A groin with hydrocele in the inguinal canal on straining was diagnosed as a CPPV and was explored bilaterally through surgery. The US findings were compared with surgical results. In 30 patients, 12 cases were diagnosed by US as patients with a CPPV, these patients underwent bilateral surgery. Eleven of 12 Cases were confirmed surgically as CPPV. From the findings of the present study it could be concluded that a PPV could be correctly detected by US in pediatric patients with the accuracy of 91.67%. US is a non invasive and accurate method for evaluating the presence of a PPV. Preoperative diagnosis of CPPV is important to remove the need for a second operation with patients presenting with unilateral inguinal hernia.