The aim of the study was to examine the relations between variables connected with the reader (interest in the text topic and willingness to read it) and the level of reading comprehension among adults, after controlling for text difficulty. The study involved 1549 users of Polish aged from 18 to 87. Open-ended questions were used to measure reading comprehension. It was proved that the model taking into account variables related to the reader better predicted reading comprehension than the model only taking into account text difficulty. Moderation analysis showed a little stronger relation between text topic interest and reading comprehension in the group of women than in the group of men. It was also noted that among adults with lower levels of education text topic interest and willingness to read it were more strongly related to the level of comprehension than among better educated people. The discussion focuses on the role of psychological factors in reading comprehension.