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To investigate the prevalence and spatial distribution of cystoid spaces (CS) in retinitis pigmentosa patients with spectral domain optical coherence tomography.A total of 529 eyes of 275 patients with retinitis pigmentosa were examined with spectral domain optical coherence tomography. The presence or absence of CS was judged for each eye. Retinal layer and outer retinal status where the CS existed were also investigated. Statistical analysis was performed using 1 eye per 1 patient.Cystoid spaces were present in 119 of 529 eyes (22.5%) of 74 of 275 patients (26.9%). There were no significant differences between the cases with and without CS except for central foveal thickness (P < 0.001). Cystoid spaces were noted in the inner nuclear layer in almost all eyes (98.6%), and outer nuclear layer/outer plexiform layer was also involved in many eyes (27.8%). Cystoid spaces were sometimes seen in ganglion cell layer (6.9%). Cystoid spaces were predominantly (78.9%) distributed in the relatively preserved retina where external limiting membrane was retained. The presence of epiretinal membrane or posterior vitreous adhesion was associated with the presence of CS (P < 0.001) but showed no relationship with the spatial location of CS (P = 1.000).The prevalence of CS in patients with retinitis pigmentosa was 26.9% and contrary to previous reports, most CS were present in inner nuclear layer. In addition, most CS were observed in relatively retained retina, which is compatible to the prevailing notion. Epiretinal membrane or posterior vitreous adhesion was also associated with the development of CS. The distribution of CS in inner and preserved retina may provide insight for the pathogenesis of CS in retinitis pigmentosa.