Inclusive jet production and jet substructure at HERA

Different aspects of jet production in the reaction e(+) + p --> e(+) + jet(s) + X with quasi-real photons have been studied with the ZEUS detector at HERA. Jets have been defined by the cone and the inclusive k(T) algorithm. Inclusive jet cross sections have been measured as a function of the jet transverse energy. They are in good agreement with next-to-leading order QCD calculations. Different features of the internal jet structure like jet shapes and subjet multiplicities have also been investigated and compared to the predictions of Monte Carlo models and theoretical calculations.