Summary: The nonlinear dynamic responses of moored crane vessels to regular waves are investigated experimentally and theoretically. The main subject of interest are nonlinear phenomena like bifurcations and the existence of multiple attractors. In the experimental part of the work, a moored model of a crane vessel has been excited by regular waves in a wave tank. A special mechanism has been developed to model the nonlinear behavior of real mooring systems. The theoretical part of the work concerns the mathematical modeling of the floating cranes. Two mathematical models of different levels of complexity are presented. Two different tools are used to systematically determine the responses of the systems to periodic forcing of waves. Firstly, the path-following techniques in combination with numerical integration of equations of motion applied to a full nonlinear model give insight into the dynamics in time domain. Secondly, the multiple scales method allows for an analytical investigation of simplified nonlinear models in frequency domain. Many results of computations for two crane vessels, barge and ship, are presented. Special attention is paid to oscillations near thef requencies of primary resonances and to subharmonic motions. An excellent agreement is found between the results of time-domain and frequency-domain analysis. The computational examples chosen correspond to the models used not only in the present experiments but in the experiments of others as well. The results presented in the work allow us to draw several important conclusions concerning the dynamic behavior of floating cranes during offshore operations. Both the developed models and the analytical tools can be used to identify the limits of the operating range of floating cranes.