A model is presented which permits the self-consistent calculations of the power deposition and velocity distribution of cyclotron resonance heated ions. The model is applied to minority heating of 3He in D-plasmas in the JET experiment. Good agreement is found between calculated and measured values of fusion yield and energy content of 3He ions. The results indicate that the power deposition is adequately described and that the fast ions slow down on electrons by Coulomb collisions. Measurements of the electron heating after the sawtooth crash show that about 50% of the energy content of the fast ions is retained in the centre after a sawtooth crash.