The numerical method for modeling of the transonic steam flows with homogeneous and/or heterogeneous condensation has been presented. The experiments carried out for the Laval nozzles, for 2-D turbine cascades and for a 3-D flow in real turbine were selected to validate an in-house CFD code adjusted to the calculations of the steam condensing flows in complicated geometries. The sensitivity of the condensation model and difficulties in the validation process of the CFD code have been discussed. These difficulties limit the possibilities of verification and improvement of the condensation theory based on the existing experimental data. The numerical simulations were based on the time-dependent 3-D Reynolds averaged Navier-Stokes (RANS) equations coupled with two-equations turbulence model (kappa-omega SST) and additional conservation equations for the liquid phase. The set of governing equations has been closed by a 'local' real gas equation of state. The condensation phenomena were modeled on the basis of the classical nucleation theory. The heterogeneous condensation model on the insoluble as well as soluble impurities was implemented into presented CFD code. The system of governing equations was solved by means of a finite volume method on a multi-block structural grid. (C) 2009 Elsevier Ltd. All rights reserved.