PEG (Percutaneous Endoscopic Gastrostomy) has become the most preferred procedure for long-term enteral feeding, since it is proven to be safe and cost effective. Pneumoperitoneum is reported to be common after PEG procedure, but the frequency of serious complications is extremely low, so conservative management is suggested. We report a case of PEG-related pneumoperitoneum and right lung atelectasis, which was not improved after 24 hours and caused respiratory distress. A 76-year-old male received PEG procedure for long-term enteral feeding. Chest X-ray taken after the procedure showed pneumoperitoneum and right lung atelectasis. Since the patient was in a stable state, we decided to observe and wait for spontaneuos resolution. But 1 day after procedure, respiratory distress and desaturation were observed, so mechanical ventilation was started. Needle aspiration of free air and intraabdominal catheter insertion were performed, and atelectasis was resolved after decompression. In our case, only right lung atelectasis was observed, so we waited for self resolution, but pneumoperitoneum and atelectasis were persisted. We decided to perform air aspiration and catheter insertion for decompression since the patient was hemodynamically unstable and his condition was deteriorating rapidly. Pneumoperitoneum may cause lung atelectasis in severe cases, and may have resulted in respiratory distress. If the possibility of respiratory distress is suspected, invasive managements including air aspiration or catheter placement should be considered.