Spectroscopic observations of Solar-System objects with ISO provided a wealth of new and exciting results. Major findings relevant to planetary atmospheres and surfaces are presented here. Rotational lines of HD were observed for the first time in the four giant planets, yielding reliable determinations of the D/H ratio. The 14N/15N ratio could also be measured in the upper troposphere of Jupiter. Many new hydrocarbons were detected in the giant planets, improving our understanding of the methane photochemistry. In addition, oxygen compounds (H2O and CO2) were detected in their upper atmospheres and in Titan, pointing to exogenic sources of oxygen. Many bands of SO2 ice were observed on Io, providing information on the physical state of this volcanic compound on the surface. Finally, spectra of Mars revealed the presence of a few so-far undetected mineralogical features, tentatively attributed to carbonates.