Purpose: To investigate changes in subfoveal choroidal thickness (SFCT) after intravitreal injections of ranibizumab for idiopathic subfoveal choroidal neovascularization (ISCNV). Methods: The prospective consecutive case series study included 16 patients with unilateral ISCNV. All eyes with ISCNV were treated with a single intravitreal injection of 0.5 mg ranibizumab followed by as-needed dosing. Subfoveal choroidal thickness was measured using enhanced depth imaging optical coherence tomography. Results: The mean total follow-up time was 4.9 +/- 1.5 months, and the follow-up after the last intravitreal ranibizumab injection was 4.4 +/- 1.3 months. In the treated eyes, the SFCT decreased significantly from 354 +/- 84 mu m at baseline to 328 +/- 79 mu m at 1 month later (P, 0.001) and reincreased (P = 0.02) to 342 +/- 75 mu m at the final visit (P = 0.15 versus baseline value). Change in SFCT was marginally (P = 0.11) associated with the change in retinal foveal thickness. In the contralateral unaffected eyes, the SFCT did not change significantly during follow-up (P = 0.76). Conclusion: In patients with unilateral ISCNV, intravitreal ranibizumab therapy was associated with a thinning of an abnormally thick subfoveal choroid, marginally in association with a parallel decrease in retinal foveal thickness. It remained elusive whether the choroidal thinning was due to a direct pharmacological effect of ranibizumab or whether it was secondary due to the foveal retinal thinning. In view of the significant differences in SFCT between affected eyes and unaffected contralateral eyes at baseline and in view of the significant therapy-associated decrease in SFCT, the potential role of SFCT as an additional marker for the diagnosis and follow-up of ISCNV and other neovascular maculopathies may be examined in future studies.