The capabilities of new methods of fusion alpha-particle diagnostics based on nuclear reactions are discussed. Particularly, the resonant capture reactions between confined fast alpha particles and low-Z artificial impurities in the plasma is examined. In this case, the intensity of the decay gamma rays is proportional to the alpha-particle concentration at resonance energy. Another method is based on Doppler shape analysis of the 4.44-MeV gamma-ray spectra from the 9Be(α, n1γ)12C reaction. Results of an in-beam study of this diagnostic reaction are given. Some questions concerning the gamma spectrometer, a collimator, and a radiation shield are discussed. Estimates of the reaction rates and signal values in the Tokamak Fusion Test Reactor, T-14, Compact Ignition Tokamak (CIT), and International Thermonuclear Experimental Reactor (ITER) are presented. In conclusion, the use of gamma spectroscopy in the diagnostics fusion protons in deuterium-deuterium plasma is examined.