A suite of coals was pretreated in steam and helium. The effect of this pretreatment on the structure and reactivity of the resulting product was examined by solvent extraction, cross-polarization magic angle spinning nuclear magnetic resonance (CP MAS NMR) spectrometry, Fourier transform infrared (FTIR) spectrometry, and steam reactivity. Hydrothermal pretreatment increased the extractive yield over that of the parent coal, indicating a likely improvement in pyrolysis yield. The effects appeared to be seam-specific rather than rank-specific. Spectral data confirmed that each coal responded differently to the treatment.