We explored whether the generalization of rules based on simple structures depends on attention. Participants were exposed to a stream of artificial words that followed a simple syllabic structure (ABA or AAB), overlaid on a sequence of familiar noises. After passively listening, participants successfully recognized the individual words present in the stream among foils, and they were able to generalize the underlying word structure to new exemplars. Yet, when attention was diverted from the speech stream (by requiring participants to monitor the sequence of noises), recognition of the individual words fell dramatically irrespective of word structure, whereas generalization depended on stimulus structure. For structures based on vowel repetitions across nonadjacent syllables (ABA; Experiment 1), generalization was affected by attention. In contrast, for structures based on adjacent repetitions (AAB; Experiment 2), generalization capacity was unaffected by attention. This pattern of results was replicated under favorable conditions for generalization, such as increased token variability and the implementation of the rule over whole syllables (Experiments 3 and 4). These results suggest a differential effect of attention on rule learning and generalization depending on stimulus structure. (Contains 1 table and 2 figures.)