Many studies suggest that long-term lexical-semantic knowledge is an important determinant of verbal short-term memory (STM) performance. This study explored the impact of emotional valence on word immediate serial recall as a further lexico-semantic long-term memory (LTM) effect on STM. This effect is particularly interesting for the study of STM-LTM interactions since emotional words not only activate specific lexico-semantic LTM features but also capture attentional resources, and hence allow for the study of both LTM and attentional factors on STM tasks. In Experiments 1 and 2, we observed a robust effect of emotional valence on pure list recall in both young and elderly adults, with higher recall performance for emotional lists as opposed to neutral lists, as predicted by increased LTM support for emotional words. In Experiments 3 and 4 however, using mixed lists, it was the lists containing a minority of emotional words which led to higher recall performance over lists containing a majority of emotional words. This was predicted by a weak version of the attentional capture account. These data add new evidence to the theoretical position that LTM knowledge is a critical determinant of STM performance, with further, list type dependent intervention of attentional factors. (Contains 5 figures and 9 tables.)