Biomass resource assessment constitutes the foundation for integrated bioenergy planning in order to evaluate the sustainable feasibility and to estimate the additional bioenergy potential. Its spatial distribution is an essential criterion to facilitate the exploitation of the untapped bioenergy potential by guiding industry and decision-making processes. This paper provides regionalized and aggregated estimates of the potentially available resources for bioenergy in Switzerland (10 woody and non-woody biomass types). First, considering the different biomass characteristics and available data, appropriate methods at the finest scale possible were elaborated to estimate the annual domestic biomass amount which could theoretically be collected. Then, explicit and rationale restrictions for sustainable bio-energy production were defined according to the current state of the art. Finally, the additional potential was estimated considering the current bioenergy production. The procedures developed can be transferred to other countries and spatial scales according to the local situation and available data. The Swiss biomass theoretical primary energy potential was estimated at 209 PJ per year, with the major contributions from forest wood (108 PJ per year) and animal manure (49 PJ per year). Almost half of the theoretical potential can be used for bioenergy in a sustainable way (26 PJ from forest wood and 27 PJ from animal manure yearly). The main restrictions are competing material utilizations, environmental factors, supply costs, as well as scattered distribution and small scale feasibility.