In the years 1985-1990, 987 patients with retinal detachment were treated in the Ophthalmological Clinic of Medical Academy in Poznań. In 25 patients, from the above group, the coexistence of retinoschisis was observed. The clinical picture of retinal detachment and retinoschisis was the basis for explaining the pathogenesis of two different phenomena: "retinoschisis versus retinal detachment" and "retinal detachment versus retinoschisis". The surgical treatment applied to 25 eyes resulted in 88% retinal attachment.