Book excerpt: The aim of this Frontiers Research Topic is to review and further explore the topic of unconscious processing in executive control. Executive control refers to the ability of the human brain – mostly associated with prefrontal cortex activity - to regulate the processing involved in the execution of novel or complex goal-directed tasks. Previous studies or models of human cognition have assumed that executive control necessarily requires conscious processing of information. This perspective is in line with common sense and personal introspection, which suggest that our choices are intentional and based on conscious stimuli. Nevertheless, in the last few years several behavioural and cognitive neuroscience studies have put under scrutiny this assumption. Cumulating evidence is now showing that prefrontal executive control can involve or be triggered by unconscious processing of information, with consequent effects on observed behaviours. One of the main methods adopted to study such unconscious mechanisms is masked priming, consisting in presenting visually masked stimuli, which nonetheless are shown to affect goal-directed behaviour or influence constructs linked to executive control and prefrontal cortex activity (e.g., task-set representation, response inhibition, conflict monitoring, error detection, reward processing, emotion regulation and task switching). This area of research is relatively young, and - while scientific evidence is emerging - no general consensus has been reached yet on how to interpret these early findings: some researchers accept that executive control can involve unconscious processing, others momentarily put aside - in first approximation - this issue, others criticize this possibility on theoretical grounds (e.g., pointing to the need of better definitions of terms such as control, conflict and consciousness) or based on experimental findings. At this stage, it appears necessary that researchers in the field make a collective effort to deepen the understanding of the unconscious mechanisms involved in executive control. This Research Topic will focus on neuroscience, but it will welcome contributions on purely behavioural and psychophysiological studies, patient reports, computational investigations, as well as philosophical and historical analyses of the relationship between executive control and consciousness. In particular, we encourage experts in this field to submit contributions in the form of: a) reviews, opinions and discussions on existing literature concerning unconscious processing of information in executive control; b) original research articles (both behavioural-only and neuroimaging studies) on unconscious processing of information in executive control; c) discussions and opinions on new methodologies to investigate this issue (e.g., other than masked priming, which has been the technique of choice in most of the existing studies).