We describe the use of simulations of experimental data in studying the behavior of hydrogen in thin layers using inverse (ρ, λ) reactions with 15N ions. Hydrogen is trapped in both disordered and epitaxial interfaces with crystalline silicon, in metal/SiO 2 interfaces, and at other sites within thin deposited layers. A simulation program has been developed which calculates the expected gamma ray yield as a function of beam energy for a specified sample structure. Such factors as the detailed shape of the resonance, Doppler broadening due to hydrogen vibrations, energy straggling of the ion beam, and background due to cosmic rays are taken into account. The sample structure is specified as a series of layers with given composition, including hydrogen content. Simulated and measured data are compared for a variety of interfaces and thin-film structures.