I assessed the occurrence of food preferences in captive squirrel monkeys and pigtail macaques and analyzed whether their preferences correlate with nutrient composition. Using a two-alternative choice test, I repeatedly presented six Saimiri sciureus and six Macaca nemestrina with all possible binary combinations of 12 types of food that are part of their diet in captivity. The two species exhibited significantly different rank orders of preference. Correlational analyses revealed that the preference ranking of the squirrel monkeys was significantly positively correlated with total energy content, irrespective of the source of energy as neither total carbohydrate content nor protein or lipid content was significantly correlated with food preference. In contrast, the preference ranking of the pigtail macaques showed a significant positive correlation with total carbohydrate content and with fructose content but not with total energy content of the food items. These results suggest that squirrel monkeys are opportunistic feeders with regard to maximizing net gain of energy, whereas pigtail macaques are not but rather seek to meet their requirements of metabolic energy by preferring foods that are high in carbohydrates.