The conformational properties of semiflexible chains of Gaussian segments are studied for a con-stant force and constant extension ensemble. Qualitative differences are found for the force-extension relation and the end-to-end distribution when the persistence length is of the order of the chain length. The comparison of the force-extension relation with experimental results on DNA molecules exhibits excellent agreement. The proposed approach provides a simple analytical expression for the end-to-end distribution which is in excellent agreement with Monte Carlo simulations of the Kratky-Porod semiflexible chain model.