The aim of this work was to examine paeroks in the Sinai Patericon which was copied in Old Russian language area in the 11–12th centuries. I was mainly searching for an answer if paeroks have got sound value in the manuscript. In the codex only “apostrophe” was used as paeroks, except handwriting V. I have concluded that paeroks in the manuscript can't have possessed sound value, which basically can be proved by the following phenomena: 1. Out of 632 cases, in 533 paeroks stand at the place of etymologically isolated position reduced vowels; in 93 cases they can be found at the place of weak position reduced ones. In my earlier researches I had already found that reduced vowels became extinct in isolated position in the codex. 2. Paeroks, except the 6 examples which can be explained with analogues never stand at the place of strong position reduced vowels. 3. Except 2 non-entire value examples, paeroks never stand at the end of words. 4. Out of reflexes of the *t?rt type sequences paeroks can only be found in c?r´k?v?, t?r´pi etc. type reflexes which cannot be accepted as a phonetic phenomenon.