Current cognitive theories of posttraumatic stress disorder (PTSD) have attributed the development of memory intrusions to specific peritraumatic visuospatial processing that occurs within working memory Empirical support has been provided by analogue trauma studies that find intrusion frequency in nonclinical participants can be significantly reduced by performance of dual tasks that place cognitive demands on the resources of visuospatial working memory (VSWM). However, it remains unclear the extent to which these reported reductions result from genuine modality-specific interference effects. The results of two experiments are reported which examine this issue using reported intrusions for affective images selected from the International Affective Picture System (TAPS). In Experiment 1 it was found that a verbal random number generation task significantly reduced the frequency of intrusions for TAPS images to the same extent as a complex visuospatial tapping task. In Experiment 2 both the modality of the dual tasks (verbal or visuospatial) and their executive load were manipulated. Only high executive load tasks were found to significantly reduce intrusion development, with no significant effect of task modality These findings do not support an interpretation of dual task effects on intrusion development in terms of modality-specific interference occurring within VSWM. Implications for current cognitive theories of PTSD and the treatment of intrusive traumatic memories are discussed.