Objective To determine whether peripheral lymphocytes and monocytes were involved in the pathological processes of coronary artery ectasia (CAE). Methods This study included 34 patients who underwent coronary angiography and were diagnosed as CAE from January 2017 to January 2018. In addition, a total of 30 patients with coronary heart disease (CHD) and 32 subjects with relatively normal coronary arteries (control group) who underwent coronary angiography on the same period were included by lot. Three groups were balanced according to age, sex, and other baseline characteristics, and the lymphocyte and monocyte subtypes in their blood samples were examined via flow cytometry. Results Lymphocyte subtypes in CAE and CHD patients showed no significant differences. However, compared to the CHD and control groups, the inflammatory (non-classic type) monocytes were significantly increased [26.45% (16.90%-44.55%) vs 13.70%(9.33%-17.60%), or 7.00% (13.70%-29.40%), P=0.000], while the classic subtype monocytes were significantly decreased [66.35% (39.73%-78.83%) vs 82.90% (80.50%-89.40%) or 78.30% (56.70%-83.80%), P=0.000] in the CAE group. Multiple linear regression analysis further confirmed that the non-classic monocyte was related to CAE [CAE group=1, CHD group=2, control group=3, so the regression coefficient is negative as β=-0.371, P=0.000 ]. Conclusions CAE could be an inflammatory disease rather than an immune disease.