The purpose of this study was to investigate the pathophysiologic change of ghrelin in gastric and colorectal cancer patients, especially in those with cachexia. Fifty-eight gastric cancer patients, 20 colorectal cancer patients, and 24 healthy control individuals were included in this study. Thirty-one patients were defined as cachectic, based on the percentage of weight loss versus the previous normal weight. The remaining 47 patients were defined as noncachectic. Peripheral hormones, including ghrelin, insulin, leptin, growth hormone, glucagon, and cortisol, and body composition parameters were measured. Plasma ghrelin levels did not increase significantly in cachectic gastric (p = 0.352) or colorectal (p = 0.871) cancer patients as compared with controls and were not correlated with nutrition status and other hormones. The location of gastric cancer (proximal vs. distal) had no influence on ghrelin levels (p = 0.966). These findings suggest that gastric and colorectal cancers may have their special effects on the production of ghrelin. Gastric or colorectal cancer cachexia may be partly due to the lack of increase in ghrelin, which makes exogenous ghrelin therapy feasible in this setting.