This article presents a lexical analysis of two types of medical texts written in Polish: hospital discharge summaries and image reports. The aim of the analysis is to assess the readability of the medical texts under investigation and its importance in the process of translation. It was assumed that the language of discharge summaries should be relatively comprehensible for a layman (patient), so that he or she could understand the description of the diagnosis and follow the instructions provided by doctors regarding post-hospital measures (such as adherence to medication regime and recommended further medical examinations). Image reports are written by experts for experts, so it can be expected that the language used in image reports is highly specialized and barely comprehensible for a patient. The pilot study has demonstrated that the discharge summaries, contrary to our assumptions, turned out to be slightly less readable for an average reader (patient) than the image reports.