The objective of the paper was to evaluate the impact of moisture in plant biomass designed for pellet production on its heating properties. The research was carried out in a pellet plant, located in Lubelskie Voivodeship. The research consisted in determination of moisture of the supplied biomass and the level of moisture of the manufactured pellet. The paper discusses the straw or hay pellet production process on the example of the selected enterprise with annual production of 60 thousand tonnes. During the period, when the tests were carried out, almost 6 thousand tonnes of raw materials i.e. grain, rapeseed, hay, camomile straw as well as a combination of straw and hay or rapeseed and rapeseed with hay were supplied to the plant. Average moisture of supplied raw materials was approximately 19%. On the other hand the manufactured heating pellet obtained moisture of approximately 14%. These values were within the range of those assumed by the company.