This paper presents the results of a forest inventory for eucalyptus plantations based on airborne laser scanner. Eucalyptus is a very fast growing plant which is mainly used for paper production in Mediterranean climate zones. A 60 km² test site was selected in Portugal, intensive field work and additional data from the forest management provided reference data for the forest inventory with laser scanner data. Since eucalyptus tree crowns within planting rows have a small diameter, the individual trees were modeled by only one parameter – the tree height. The verification of the results from the automatic single tree detection showed a correctness of 93 %. For the estimation of the timber volume for each stand a single tree approach in combination with a stand wise approach was used. The calculation of timber volume for several reference stands with a total size of 75 ha yielded to a correctness of again 93 %. Finally all developed methods were implemented as additional tools in the Joanneum Research image processing toolbox IMPACT. Within IMPACT a processing chain was established which enables an automatic calculation of timber volume for eucalyptus plantations based on a digital terrain model, GIS information of the stands and first pulse laser scanner raw data.