It is established that the prefrontal cortex (PFC) and visual area V4 are part of a network, critical for the deployment of attention. Despite progress emphasizing the importance of patterns of collective activity in cognition, the influence of attention on population dynamics is not clear. Interestingly, neurons in association cortices have been reported to exhibit mixed selectivity, yet its contribution to the population code during attention is poorly understood.To investigate the influence of spatial attention on patterns of population activity, we performed extracellular recordings in the ventrolateral PFC and V4 of two monkeys during a cued spatial attention task. We employed population-level approaches to assess the population code structure before and after attentional deployment.We found that PFC and V4 exhibit distinct patterns of collective activity before and after attentional deployment. In PFC, stimulus representations during attentive states were orthogonal to those during sensory states. Contrary, V4 representations during sensory and attentive states exhibited substantial overlap. Projecting population activity onto the sensory and attention decoding axes revealed distinct selectivity clusters. Specifically, we found subpopulations selective for sensory, attention or both epochs. In PFC only, selectivity in the latter subpopulation appeared to be dynamic, with each neuron’s contribution to the decoding axis being influenced by attention. Overall, our results provide novel insights into how attention shapes the population code in different regions.Funding: Hellenic Foundation for Research and Innovation, “Basic Research Financing (Horizontal support for all Sciences), National Recovery and Resilience Plan (Greece 2.0)” (Project: 14941), EU NextGenerationEU.