Studies on the neurobiological background of anxiety indicate that the patogenesis of anxiety may be related to the process of an extinction of aversive memories. It has been suggested that disruption of selective attention for emotional stimuli may confer the risk for mental disorders, such as phobias and post-traumatic stress disorder, PTSD. Differences in the effects of local neuronal and hormonal activities of the HPA axis on emotional memory formation, might underlie individual differences in the emotional reactivity. Studies on molecular and cellular mechanisms responsible for individual fear extinction may serve as the basis of search for more effective forms of clinical treatment of anxiety. Behavioural therapy of phobias and PTSD can be facilitated by D-cycloserine (the agonist at the glycine site of the NMDA receptor), ligands stimulating endogenous cannabinoid system and by gluocorticosteroids. Although all these substances stimulate different central mechanisms, they appear to act synergistically, to improve the behavioural therapy.