The article presents the research project of the electronic Conceptual Dictionary of Old Polish (Słownik pojȩciowy jȩzyka staropolskiego) prepared in the Institute of Polish Language at the Polish Academy of Sciences in Cracow. This dictionary is based on The Old Polish Dictionary and The Supplement (Verba absentia), part I. The Conceptual Dictionary of Old Polish which includes the oldest known Polish vocabulary - from the beginning of the Polish language to the end of the fifteenth century. The main aim of this project was to assign each lexical unit to the separate conceptual categories. The semantic structure of this dictionary is based on a hierarchical system created by R. Hallig and W. von Wartburg. This dictionary also contains the grammatical and structural classification of medieval vocabulary. The Conceptual Dictionary of Old Polish has 22 735 entries, and within 54 038 lexical units. Each meaning and function is illustrated by one example given in transliteration and in transcription. © 2016 Society of Friends of the Polish Language. All rights reserved.