In some languages, such as in English, Russian, Dutch and Icelandic, children show mastery of the comprehension of reflexives from a relatively early age, but they still have problems interpreting pronouns until the age of 6 and 7. This problem only manifests itself in comprehension, and it is called the Pronoun Interpretation Problem (PIP). In my thesis I elaborate on some significant child language experiments related to the PIP, and I represent the possible explanation for the phenomenon. I mostly discuss research on English, but I also touch upon the reasons for cross-linguistic variations. I dedicate a section to represent the case of Hungarian, as well.