Chemical composition of cigarette smoke has been extensively researched in the past mostly using off-line methods such as GC/MS or HPLC. Often the smoke was already aged and altered by the sampling/trapping when it was analyzed. It is known that many substances in smoke build up and decay as the smoke ages. For most, if not all, of the health relevant chemicals in smoke, there is no reliable data on the concentrations at the point they enter the smoker's respiratory tract. There is thus a major need for rapid on-line monitoring of toxic compounds in cigarette smoke to investigate their formation mechanisms and dynamic fluctuations. Especially studying the influence of the smoking behaviour of human smokers on the formation of toxic compounds is particularly interesting. Laser mass spectrometry, based on resonance multiphoton ionization (REMPI) and single photon ionization (SPI) combined with time-of-flight mass spectrometry (TOFMS) has been proven to be a valuable tool for the direct real time analysis of health relevant smoke components in main- and sidestream smoke. These analytical methods have been applied for the puff-by-puff resolved analysis of inhaled smoke (mouthspace analysis). This required the development and characterisation of a new sampling setup for the inhaled/ exhaled smoke or breath-air with SPI/REMPI-TOFMS. Cigarettes containing tobaccos exhibiting different tar and nicotine content ("Light" and "Full Flavour") are smoked by test persons and the time dependent trends of selected Hoffmann analytes are recorded in the inhaled or exhaled smoke. Furthermore breath analyses of smokers and non-smokers were performed. In the lecture first mouth space analysis and breath analysis data is shown and interpreted.