AIM: To evaluate central macular thickness(CMT) and mean choroidal thickness(MCT) in eyes with branch retinal vein occlusion(BRVO), before and after ranibizumab treatment using spectral domain-optical coherence tomography(SD-OCT).·METHODS: Forty-two patients with unilateral BRVO and macular edema were included in this study. There were 25 men and 17 women. Using SD-OCT, choroidal thickness was measured at 500 μm intervals up to 1500μm temporal and nasal to the fovea. MCT was calculated based on the average of the 7 locations. All the eyes with BRVO were treated with intravitreal ranibizumab(0.5 mg/0.05 m L). Comparisons between the BRVO and fellow eyes were analyzed using Mann-Whitney U test. Preinjection and post-injection measurements were analyzed using Wilcoxon test and repeated measure analysis.· RESULTS: At baseline, there was a significant difference between the BRVO and fellow eyes in MCT[BRVO eyes 245(165-330) μm, fellow eyes 229(157-327) μm]and CMT [BRVO eyes 463(266-899) μm, fellow eyes 235(148-378) μm(P =0.041, 0.0001, respectively)]. Following treatment, CMT [295(141-558) μm] and MCT [229(157-329) μm] decreased significantly compared to the baseline measurements(P =0.001, 0.006, respectively).Also BCVA(log MAR) improved significantly(P=0.0001) in the BRVO eyes following treatment. After treatment CMT[BRVO eyes 295(141-558) μm, fellow eyes 234(157-351) μm]and MCT [BRVO eyes 229(157-329) μm, fellow eyes 233(162-286) μm] values did not reveal any significant difference in BRVO eyes and fellow eyes(P=0.051, 0.824,respectively).· CONCLUSION: In eyes with BRVO, CMT and MCT values are greater than the fellow eyes, and decrease significantly following ranibizumab injection.