Background: The postoperative pain in children and adolescents is most commonly managed by intramuscular injections of NSAIDs or opioids. This approach may result in fluctuating plasma drug levels and cycles of pain, comfort, and sedation. Patient-controlled analgesia(PCA) is a method of analgesia administration that consists of a computer-driven pump with a button that the patient may press to administer a small dose of analgesic drug. Materials & Methods: Forty ASA physical status 1 or 2 children and adolescents were divided into two groups. In the PRN group, patients received intramuscularly diclofenac(Valentac$^{(R)}$) on a p.r.n. basis. The PCA group patients received a mixture of nalbuphine and ketorolac by WalkMed$^{(R)}$PCA infusor. Analgesic efficacy was evaluated with NRS(numerical rating scale) and Faces Pain Rating Scale. The side effects were evaluated. Results: The patients of PCA group had less pain than those of PRN group. Complications were similar in both group. Conclusions: PCA with nalbuphine and ketorolac is a safe and effective methods of pain relief in children and adolescents after surgery, and is better accepted than intramuscular injections.