The course of PTSD is often chronic and impedes individual's functioning. Subjective reports of sleep disturbance indicate that 70-91% of patients with post-traumatic stress disorder (PTSD) have difficulty falling or staying asleep. Nightmares are reported by 19-71% of patients, depending on the severity of their PTSD and their exposure to physical aggression. Paroxetine is a potent and selective inhibitor of the neuronal reuptake of serotonin, effective in PTSD. Mirtazapine is a noradrenergic and specific serotonergic antidepressant, its primary use is the treatment of major depressive disorder and other mood disorders and it is helpful in PTSD by suppressing nightmare activity or in blocking the memory of the dream state upon awakening. Mirtazapine's unique mechanism of action may account for its success in augmentation. Combining mirtazapine with a SSRI has been shown to be superior to antidepressants alone and improve sleep in patients with PTSD.The purpose of present study was to asses efficacy and tolerability of augmentation of paroxetine with mirtazapine in PTSD. It is single centre, nonrandomized, open-label, parallel group study, in 20 inpatients diagnosed as PTSD, according to ICD-10 Classification, received paroxetine alone (30-40 mg AM.) or in combination with mirtazapine (30-45 mg b.t.). Subjects were divided into two groups-paroxetine group (13) and paroxetine/mirtazapine group (17). Paroxetine as monotherapy or combined with mirtazapine is effective and safe in treatment of PTSD, however, mirtazapine co-therapy might produce a more rapid response, with the positive result of this use of mirtazapine for this disorder, given the devastating effects of the nightmares and sleeplessness caused by catastrophic stress.