NOVELTY - Producing a hydrocarbon composition, comprises: providing a biomass raw-material; gasifying the raw-material; removing at least an essential part of the impurities to produce a clean syngas; feeding the clean syngas to a Fischer-Tropsch reactor; converting in the Fischer-Tropsch reactor at least a significant part of the carbon monoxide and hydrogen contained in the syngas into a hydrocarbon composition; and recovering from the Fischer-Tropsch reactor a hydrocarbon composition.    USE - The method is useful for producing a hydrocarbon composition (claimed).    ADVANTAGE - The method is highly improved and efficiently produces hydrocarbon compositions of the kind which can be used in the production of fuel for combustion engines.    DETAILED DESCRIPTION - Producing a hydrocarbon composition, comprises: providing a biomass raw-material; gasifying the raw-material by oxygen-blown gasification to produce a raw syngas containing carbon monoxide, carbon dioxide, hydrogen, hydrocarbons and gaseous and particulate impurities, the raw syngas having a hydrogen-to-carbon monoxide ratio of 0.5-1.7; removing at least an essential part of the impurities to produce a clean syngas; feeding the clean syngas to a Fischer-Tropsch reactor; converting in the Fischer-Tropsch reactor at least a significant part of the carbon monoxide and hydrogen contained in the syngas into a hydrocarbon composition containing C4-C90 hydrocarbons; recovering from the Fischer-Tropsch reactor a hydrocarbon composition which mainly contains hydrocarbons which are solid or semisolid at ambient temperature and pressure; where the hydrogen-to-carbon monoxide ratio of the syngas is being raised to about 2.0 at the latest when the syngas is fed into the Fischer-Tropsch reactor, characterized by the combination of: separately recovering from the Fischer-Tropsch reactor an off-gas comprising hydrocarbons which are gaseous at ambient temperature and pressure; separately producing hydrogen from the gaseous hydrocarbons of the off-gas; and feeding at least a part of the hydrogen gas thus produced into the clean syngas in order to increase the hydrogen-to-carbon monoxide ratio of the clean syngas.