Many molecular species are only available in complex mixtures or very low concentrations. This restricts application of laser spectroscopy. An important tool to cope with this problem is additional mass selection. The combination of pulsed lasers, time-of-flight mass analyzers, supersonic beams, as well as multiphoton absorption and secondary laser excitation supplies new methods and applications for molecular spectroscopy. Exemplary results of our group are presented, such as UV-spectra of molecular cations, Rydberg and photoelectron spectra, ZEKE spectra of molecular anions, first well resolved UV-spectra of several neutral molecules and the application of mass selective laser spectroscopy to environmental trace analysis.