The applicability of 7-hydroxycoumarin-3-carbonitrile (1) and 7-hydroxycoumarin-3-carboxylic acid (2) as fluorescent probes for monitoring of cationic photopolymerization processes by fluorescence probe technique (FPT) was evaluated in comparison to the response of 7-diethylamino-4-methylcoumarin (C1). Triethylene glycol divinyl ether and diphenyliodonium hexafluorophosphate were used as an example monomer and a cationic photoinitiator, respectively. It has been found that the probe 1 withstands the cationic polymerization conditions and provides correct probe response. The probes 2 and C1 undergo side reactions under the cationic polymerization conditions that make them unusable for monitoring of the polymerization progress at high monomer conversions. The application of 1 as an amine-free probe for monitoring of curing progress of photocurable coatings cured by cationic photopolymerization is proposed. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013