The present paper overviews properties of implicit knowledge discovered in cognitive psychology and describes their relevance for cognitive behavior therapies. It shows, first, that implicit structures are learned by direct exposure to environments or stimuli governed by a structure or by acting/responding according to a structure. Second, one can develop both conscious and unconscious knowledge regarding a structure, and, third, implicit structures themselves can generate conscious knowledge. Hence, these conscious contents might mask sometimes the presence of unconscious structures. Fourth, implicit structures can be counteracted by alternative structures, but they cannot be erased. Consequently, they can be subactivated, but they can re-activate in some circumstances. Fifth, implicit structures are learned better in childhood and adolescence. Moreover, the paper suggests several directions of research that could clarify the role of implicit structures in CBTs and, more generally, in psychopathology and human adaptation.