Abstract: AIM:To observe the effects of coronary heart disease (CHD) and depression on the platelet activity in elderly patients. METHODS: According to WHO diagnostic criteria for coronary heart disease and Zung self-rating depression scale (SDS), subjects in this study were divided into four groups: non-depressed and non-CHD group (n=87), CHD non-depressed group (n=94), depression without CHD group (n=85), and CHD and depression group (n=97). Platelet count (PLT), mean platelet volume (MPV), and platelet distribution width (PDW) were detected. RESULTS: There was a significant difference in PLT, MPV and PDW between non-depressed and non-CHD group and the other three groups, and PLT, MPV and PDW values were higher in the other three groups. The increase and decrease in regard to the value of PLT, MPV and PDW are not obvious in the non-depressed CHD group and the depression without CHD group. No significant difference was found in the two groups. A significant difference was found in MPV and PDW but no significant difference was seen in PLT. The rise and fall in regard to the value of PLT is not obvious, but MPV and PDW are higher between CHD non-depressed group with CHD and depression group, and between depression without CHD and CHD and depression group. CONCLUSION: Coronary heart disease and depression both may increase platelet activity, and CHD plus depression may further increase platelet activity.