The detrimental effect of increased memory load on selective attention has been demonstrated in many situations. However, in search tasks over time using RSVP methods, it is not clear how memory load affects attentional processes; no effects as well as beneficial and detrimental effects of memory load have been found in these types of tasks. The main objective of the present work is to provide more evidence about the involvement of working memory in visual search over time. Using an RSVP search task, we manipulated set size (experiment 1) and congruency in a Stroop-like task (experiment 2), finding that high memory load conditions sometimes increase the efficiency of search over time. Our data also support important similarities between attention in space and time showing that there might be a general system for allocating attentional resources independent of stimulus dimension. However, there are also important differences, thus theoretical implications of present results are discussed.