PURPOSE:This study was designed to compare metabolic and functional results after laparoscopic and open colorectal resection.METHODS:Seventy‐nine patients were randomly assigned to laparoscopic (n = 40) or open (n = 39) colorectal resection. Before and after operation, the following parameters were determined: respiratory function (spirography and blood gas); serum level of cortisol, lactate, and C‐reactive protein; total lymphocyte count; and CD4 and CD8 lymphocyte subsets. Intraoperative core temperature was measured by a bladder probe. Postoperative pain and analgesic consumption were also monitored.RESULTS:Mild operative hypothermia, a trend to postoperative reduction of total lymphocyte count, and significant impairment of respiratory function early after surgery were found in both groups. Laparoscopy showed a higher CD4/CD8 ratio (P= 0.01) on postoperative Day 1 and a faster return of C‐reactive protein to preoperative values (P= 0.01) than in the open colorectal resection group. Morphine consumption in the first 48 hours after surgery was lower in the laparoscopic than in the open group (P= 0.02).CONCLUSIONS:Laparoscopy was associated with a less pronounced immunosuppression and inflammatory response and a lower consumption of analgesic drugs than open surgery. Moreover, our data did not show any additional detrimental effect of laparoscopy on either operative core temperature or early postoperative respiratory function.