It is known that pediatric inguinal hernia is caused by the incomplete closure of processus vaginalis (PV). In the case of unilateral hernia, possibile contralateral patent PV should be considered because of its delayed appearance as well as its risk of incarceration. Direct visualization of patent PV could be done by contralateral exploration or by indirect exploration through the ipsilateral opening site of the affected hernia assisted with laparoscope. A patient group (321 persons) to whom laparoscopy was not performed from March 2000 to March 2003 was analyzed and compared with a patient group (280 persons) to whom laparoscopy was performed from April 2003 to September 2005. With all 601 patients, the sex ratio (male/female) of patients was 3.8:1. The side distribution was 57.7% in the right, 32.1% in the left and 10.1% in bilateral. There was no difference of sex and side distribution between before and after laparosopy adoption. We did not find an age correlation in natural closure of the residual PV of the peritoneum. Contralateral hernia developed in 14 persons (2.5%) after the operation of unilateral inguinal hernia before laparoscope adoption. But no contralateral hernia developed after April 2003 with laparoscopy. We think that if we use laparoscopy, being a safe and accurate method, to check whether the contralateral residual PV is opened or closed, possible future contralateral operation can be avoided.