A process for converting an olefin feed to hydrocarbons suitable for fuel components or their feedstock. According to the process, an olefin feed, possibly together with another hydrocarbon feed, is contacted in a reactor with a catalyst in order to produce a hydrocarbon having at least one alkyl side chain. In the invention, the olefin feed is contacted with a particle-form fluidized catalyst in a circulating-bed reactor, wherein the catalyst forms the circulating bed of the reactor. When the operation is carried out in a circulating-bed reactor, the retention time of the feedstock is short. In this case, iso-olefins are formed quite selectively from n-olefins in isomerization. Since the useful life of the catalyst lengthens while the catalytic activity of the bed remains high for a long time, the conversion level also remains high. A long useful life of the catalyst is an economically highly significant advantage. In a circulating-bed reactor the regeneration of the catalyst can be carried out quite flexibly, and the operation of the reactor need not be interrupted for the duration of regeneration.