Background: Laparoscopic cholecystectomy is a way of removing the gallbladder. But like other surgeries, this procedure has some side effects such as postoperative shoulder pain. This study evaluates the effect of different gas flow rates into the abdominal cavity on postoperative shoulder pain in laparoscopic cholecystectomy patients. Methods: The study as a randomized clinical trial was conducted on laparoscopic chol-ecystectomy patients in Imam Khomeini Hospital- Esfarayen 2011-2012. One hun-dred participants were selected by available sampling, and were divided randomly into two groups of 50 patients. In group I flow rate of CO2 gas was two liters per minute and in group II flow rate of CO2 gas was five liters per minute. After reversing anesthe-sia, six, 12 and 24 hours post operative, shoulder pain was evaluated by Visual Ana-logue Scale (VAS) pain questionnaire. The study findings analyzed by independent t-test. Results: The mean age of participants was 48.8±7.5 years and mean surgery duration was 36.5±13.1 minutes, and there was no significant differences between two groups (P>0/05). However, the mean shoulder pain scores in group I (blowing with low pres-sure) was differed significantly with group II (blowing with high pressure) (P<0.05). In group I, pain was lower than group II. Conclusion: Results showed if CO2 gas flow rate is two liters per minute (blowing with low pressure), the patients complain less shoulder pain. Therefore low pressure gas in-sufflation for laparoscopic surgery is recommended. Further studies in this field should be considered.