Objective To observe the choroidal thickness of patients with chronic central serous chorioretinopathy (CSC) in affected eyes and unaffected fellow eyes.Methods Forty-five chronic CSC patients diagnosed by fundus pre-set lens, fundus fluorescein angiography (FFA) and indocyanine green angiography were enrolled in this study. The patients included 36 males and nine females, with a mean age of (46.18plusmn;8.20) years, with a mean duration of (16.34plusmn;7.23) months. Thirty-six patients were affected unilaterally and nine patients affected bilaterally. The patients were divided into affected eyes group (group A, 51 eyes) and unaffected fellow eyes group (group B,39 eyes). Fifty age-, sex- and diopter- matched normal subjects (50 eyes) were enrolled in this study as control group (group C). Enhanced depth imaging (EDI) choroidal scans were obtained in all eyes by using spectral-domain optical coherence tomography. Subfoveal choroidal thickness (SFCT) and choroidal thickness at 3 mm nasal (NCT3 mm), temporal (TCT3 mm), superior (SCT3 mm), inferior (ICT3 mm) to the fovea were measured.Results The mean SFCT of group A, B and C were (436.76plusmn;87.01), (394.71plusmn;61.63), (294.86plusmn;75.30) mu;m respectively. The mean SFCT of group A and B were thicker than group C, the difference was significant among three groups (F=44.791,P＜0.001). There were difference between group A, B, C in NCT3 mm, TCT3 mm, SCT3 mm and ICT3 mm (F=15.816, 22.823, 15.147, 11.527;P＜0.001). The mean SFCT in affected eyes of unilateral patients was (416.34plusmn;79.44) mu;m, which was thicker than that in unaffected fellow eyes (t=2.897, P=0.007). Conclusion Choroidal thickness increased significantly in affected eyes and unaffected fellow eyes in patients with chronic CSC.