Dietary fiber, maintaining the gut environment, contributes to better lung function among smokers. This study was aimed to investigate the role of dietary fiber on the anti-oxidant capacity and gut environment during exposure to cigarette smoke. The anti-oxidant capacity as well as caecal levels of organic acids and population of micro-flora in the gut was measured after 4 months’ exposure to cigarette smoke in mice (C57BL/6NcrSlc) fed with a cellulose-free diet. Animals were divided into control diet (AIN-93G)/non-smoke, cellulose-free diet/non-smoke, control diet/smoke, and cellulose-free diet/smoke groups. The anti-oxidant capacity in plasma was significantly suppressed by the cellulose-free diet in the non-smoke exposed mice. The suppression in the anti-oxidant capacity further declined following exposure to cigarette smoke. Both these changes in the anti-oxidant capacity were accompanied with changes in some organic acids levels in caecal contents. The anti-oxidant activity was significantly inversely correlated to succinic acid / acetic acid levels balance in caecal contents. In conclusion the cellulose-free diet suppressed the anti-oxidant capacity in mice, and the suppression further decreased by exposure to cigarette smoke. These changes in the anti-oxidant capacity may be related with changes in the gut environment.