Purpose. To describe topographical changes in choroidal thickness as measured by optical coherence tomography following photodynamic therapy (PDT) for central serous chorioretinopathy (CSC). Methods. Case report. Results. By 1 month following PDT, mean (SD) choroidal thickness decreased from 562 microns (24) to 424 microns (27) (P < 0.01) at 3 mm temporal to fovea, 483 microns (9) to 341 microns (21) (P < 0.01) at 1.5 mm temporal to fovea, 576 microns (52) to 370 microns (81) (P < 0.01) under the fovea, 442 microns (30) to 331 microns (54) (P < 0.04) at 1.5 mm nasal to fovea, and 274 microns (39) to 171 microns (17) (P < 0.01) at 3 mm nasal to fovea. The Location of greatest choroidal thickness (648 microns) prior to treatment was at point of leakage on fluorescein angiogram (FA). This region decreased to 504 microns following treatment. Conclusion. A decrease in choroidal thickness can be seen following PDT for CSC as far as 3 mm temporal and 3 mm nasal to fovea. The Location of greatest choroidal thickness may be at point of leakage on FA.