The experiment aiming to compare the humidity of two Salix viminalis clones and Sida hermaphrodita biomass was carried out in 2003–2004. The humidity was compared among four harvest dates and three-month storage period in 2003. In 2004, only one harvest date was realized. Regardless of the harvest date, the Salix viminalis biomass humidity exceeded 50%, and it increased up to 66–68% after three months of storage. Sida hermaphrodita in November contained 49%, while that harvested in subsequent harvest dates – over 70% dry matter. No significant differences were found in dry matter yields of Salix viminalis and Sida hermaphrodita.