Both the particle based Direct Simulation Monte Carlo (DSMC) method and a compressible Navier-Stokes based continuum method are used to investigate the flow inside micronozzles and to predict the performance of such devices. For the Navier-Stokes approach, both slip and no-slip boundary conditions are applied. Moreover, the two methods have been coupled to be used together in a hybrid particle-continuum approach: the continuum domain was then investigated by solving the Navier-Stokes equations with slip wall boundary condition, whereas the region of rarefied regime was studied by DSMC. The section where the domain was split was shown to have a great influence in the prediction of the nozzle performance.