Abstarct: Codling moth, apple ermine moth and plum fruit moth are the most destructive and most important pests of apple and plum gardens around the world and are known as one of the most damaging pests. Insects use cellular and humoral defense against pathogens, parasitoids, and environmental stresses. The role of hemocytes and the phenoloxidase system has been proven in insects cellular defense. The number of hemocytes is affected by any type of tension or entry of the foreign agent to the hemolymph. Insects with a strong immune system sometimes can change the pathogenicity of a pathogenic agent or stop it. Due to the role of hemocytes as a key factor has been proven in immune system of insects, therefore identification of the types of insect hemocytes is the first step in recognition of comprehensive features of immunologycal. In this study, hemocytes of fifth instar larvae of Cydia pomonella L., Yponomeuta malinellus Zell. and Grapholita funebrana Treitsch were studied by using of light microscopy at 40x magnification. Cells were identified by Giemsa staining. Five types of hemocytes were identified in larvae of these insects that including: granulocytes (GRs), plasmatocytes (PLs), oenocytoids (OEs), prohemocytes (PRs) and spherulocytes (SPs). Also the frequency of hemocytes,the frequency of immunocytes, the phenoloxidase enzyme activity, and the weight of fifth instar larvae of any three pests were investigated. The results showed that there was a significant difference in the number of granulocytes, prohemocytes, oenocytoids, spherulocytes and immunocytes of codling moth, apple ermine moth and plum fruit moth. Granulocytes and plasmatocytes were the most abundant cells in any three pests. However, the highest number of granulocytes was observed in the hemolymph of apple ermine moth and the highest number of plasmatocytes was observed in plum fruit moth. The concentration of prohemocytes and oenocytoids was more abundante in codling moth than apple ermine moth and plum fruit moth. The amount of phenoloxidase enzyme activity of any three pests was measured in the presence of L-DOPA substrate and there was no significant difference between them. The weight of fifth instar larvae of apple ermine moth, was significantly higher than other larvae. Recognition of the pests physiology like biology, is important and essential to control them. Therefore, with accurate recognition of hemocytes and their frequency and also study of the amount of phenoloxidase enzyme activity, aspects physiological defense of insects could be better checked and use microbial control methods against them