AIM: To assess the correlation between choroidal thickness (CT) and the early stages of diabetic retinopathy (DR) in type 2 diabetic patients. METHODS: We divided 83 diabetic patients (51-80 years of age; 50 females) into non diabetic retinopathy group (NDR) and mild/moderate nonproliferative diabetic retinopathy (NPDR) group, and compared them with 26 non-diabetic control subjects (51-78 years of age; 16 females). Subfoveal choroidal thickness (SFCT) and parafoveal choroidal thickness (PFCT) were measured using enhanced depth imaging spectral-domain optical coherence tomography (EDI-OCT). Ocular health status, disease duration, body mass index, and hemoglobin A1c (HbAlc) were recorded. RESULTS: The mean ages of the NDR, NPDR, and control groups were 68.0 +/- 6.9y, 67.8 +/- 6.4y, and 65.1 +/- 6.3y, respectively (P=0.17). Pearson correlation of the right and left eyes for the control subjects was 0.95 and for the NDR subjects was 0.93. SFCT for the right eyes of the controls was 252.77 +/- 41.10 mu m, which was significantly thicker than that of the right eyes in NDR group (221.51 +/- 46.56 mu m) and the worse eyes of the NPDR group (207.18 +/- 61.87 mu m; ANOVA, P<0.01). In the diabetic patients pooled together, age was the only variable significantly associated with SFCT (multiple linear regression analysis, P=0.01). CONCLUSION: CT decreased significantly in the NDR and mild/moderate NPDR eyes compared with the control eyes. Age is significantly associated with SFCT in the diabetic patients. Diabetic choroidopathy may be present before clinical retinopathy.