Brand managers face a well-known conundrum when it comes to TV advertising planning: deciding when and where to air their ads to enhance advertising response. They can choose to diversify by airing ads at different times (temporal diversification) and across various networks (spatial diversification. Alternatively, they can follow a more focused approach by airing ads in a shorter time window or only on specific networks. However, despite the importance of this issue to managers, empirical knowledge on the relative effectiveness of differentiation vs focus in terms of when and where to air ads is limited. To address this gap, the authors investigate the effects of temporal and spatial diversification on the different stages of the purchase funnel (i.e., ad awareness, brand impression, consideration, and purchase intent) and examine the moderating effects of consumption purpose and brand size. Using a sample of 195 brands across 33 categories over a period of 252 weeks (four and a half years), the study shows that temporal and spatial diversification yield different results and that effects depend on category and brand factors. These findings provide valuable insights for brand managers seeking to optimize their TV advertising planning and contribute to the broader literature on advertising effectiveness.