Do creative ad executions like large ad sizes and intrusive ad formats that enhance communication outcomes and clickthroughs immediately after ad exposure persist over time? In examining this question, we focus on the role of advertisement size (large vs. small) and ad exposure format (intrusive vs. voluntary) on immediate and delayed brand recall, ad recognition and brand attitude in web-based media. Voluntary exposure ad formats like banners and text ads are more likely to be cognitively avoided since it is an automatic, subconscious process that occurs in parallel with the browsing activity and does not require any behavioral action by the consumer. Intrusive ad formats like pop-ups that interrupt browsing activity and demand immediate response are more likely to be physically avoided by closing them. Prior research on preattentive processing and endurance of implicit/ explicit memory and memory for subgoals supports our findings that gains from using intrusive ads accrue when ad sizes are small and negative impact of intrusiveness decay over time.