Laser-induced resonance-enhanced multi-photon ionization (REMPI) represents an efficient and highly compound selective (even isomer discrimination can be achieved) ionization method and therefore is ideally adapted as an ion source for analytical time-of-flight mass spectrometry (TOFMS). The combination of mass and optical selectivity (high-resolution UV spectroscopy is involved in the REMPI-ionization process), its high sensitivity, and the high measurement speed makes the REMPI/TOFMS approach a powerful tool for on-line emission control of combustion processes. A REMPI/TOFMS-based monitor for highly time resolved analysis (sampling rate 50 Hz) of organic and inorganic compounds in the exhaust gas of internal combustion engines is already in operation; an exhaust-gas measurement is presented in the paper. However, recent investigations focus on the question of whether the REMPI/TOFMS technique combined with a supersonic Jet-inlet system (Jet-REMPI/TOFMS) is also applicable for continuous realtime monitoring of highly toxic combustion trace products. Relevant examples are polycyclic aromatic hydrocarbons (PAH, e.g., benzo[a]pyrene) and chlorinated aromatics (e.g., chlorinated dibenzo-p-dioxins/furans, PCDD/F). Such an on-line monitor is currently needed for emission control of industrial combustion processes as, for example, waste incineration (WI) facilities. In addition to some technical improvements (e.g., increase in on-line sensitivity or coupling with gas chromatography), one major prerequisite for practical applications is a thorough knowledge of the spectroscopic properties of the relevant target compounds. This contribution focuses on these spectroscopic preconditions. In conclusion, concepts for an on-line emission monitoring of the PCDD/F-content in flue gases of WI plants by means of the Jet-REMPI/TOFMS technique are presented. They are based on either the indicator parameter relationship between, for example, chlorinated benzenes and PCDD/F in the WI-exhaust gases (real-time, on-line technique) or a fast, repetitive discontinuous trapping and enrichment before a fast gas chromatography-Jet-REMPI/TOFMS detection.