English word-initial vowels in natural continuous speech are optionally preceded by glottal stops or functionally equivalent glottalizations. It may be claimed that these glottal elements disturb the smooth flow of speech. However, they clearly mark word boundaries, which may potentially facilitate speech processing in the brain of the listener. The present study utilizes the word-monitoring paradigm to determine whether listeners react faster to words with or without glottalizations. Three groups of subjects were compared: Czech and Spanish learners of English and native English speakers. The results indicate that perceptual use of glottalization for word segmentation is not entirely governed by universal rules and reflects the mother tongue of the listener as well as the status (L1/L2) of the target language.