PURPOSE: To compare the efficacy and safety of half-fluence photodynamic therapy (PDT) and conventional PDT in chronic central serous chorioretinopathy. METHODS: A multicenter retrospective comparison study. Retrospective review of 60 patients including 29 patients (34 eyes) who received half-fluence PDT and 31 patients (33 eyes) who received conventional PDT for the treatment of chronic central serous chorioretinopathy. Best-corrected visual acuity, central fovea retinal thickness and resolution of subretinal fluid on optical coherence tomography, and choroidal perfusion decrease on indocyanine green angiography were assessed. Choriocapillaris perfusion decrease was quantified as mean gray value ratio of treated and nontreated areas using commercial imaging software. RESULTS: Treatment success without recurrence was achieved in 32 of 34 eyes (94.1%) treated with half-fluence PDT and 33 of 33 eyes (100%) treated with conventional PDT (P = 0.493). There was no difference in final best-corrected visual acuity (logarithm of the minimal angle of resolution) between the 2 groups (0.17 ± 0.32 vs. 0.21 ± 0.39; P = 0.603). Choriocapillaris perfusion decrease quantified from post-PDT indocyanine green angiography was significantly more severe in the conventional PDT group (P = 0.006), and it showed a positive correlation with retinal thinning after PDT (R = 0.380; P < 0.001). CONCLUSION: Half-fluence PDT is as effective as conventional PDT, while minimizing the deleterious effect on choriocapillaris perfusion and retinal thickness.