Disagreement exists about whether lexical selection in word production is a competitive process. Competition predicts semantic interference from distractor words in immediate but not in delayed picture naming. In contrast, Janssen, Schirm, Mahon, and Caramazza (2008) obtained semantic interference in delayed picture naming when participants had to decide between picture naming and oral reading depending on the distractor word's colour. We report three experiments that examined the role of such task decisions. In a single-task situation requiring picture naming only (Experiment 1), we obtained semantic interference in immediate but not in delayed naming. In a task-decision situation (Experiments 2 and 3), no semantic effects were obtained in immediate and delayed picture naming and word reading using either the materials of Experiment 1 or the materials of Janssen et al. (2008). We present an attentional account in which task decisions may hide or reveal semantic interference from lexical competition depending on the amount of parallelism between task-decision and picture-word processing.