Experiments on visualization of unreadable manuscript marginalia (fading of ink, spreading of ink, crossed out ink, scraping of ink, gluing with restoration materials) of several copies of the Ostrog Bibles from the National Library of  Russia and the Library of Russian Academy of Sciences using hyperspectral imaging have been conducted. The aim of work was to find a way using advanced opto-electronic techniques to read invisible marginalia. In experiments  NIR hyperspectral camera operating in the range 400–1100 nm and original self-developed software were used. Marginalia have been visualized by means of hyperspectral imaging that made possible to recognize badly visible texts  and bring new information for art historians.