The prescription of psychotropic drugs during paediatric age is now widely debated, since the utilization of drug therapy has consistently increased together with mental health difficulties in youngsters under 21 years of age. Acccording to the WHO, in Europe about the 10% of children is affected by behavioural disorders, and in particular the 2% of children and 18% of adolescents are affected by depressive syndrome. In the last decade, in Italy 2 children over 1000 have taken antidepressants belonging to Serotonin Selective Reuptake Inhibitors class. The few double-blind-placebo related controlled studies has shown an effectiveness of this class of antidepressants, although an augmented risk for suicidal behaviour has been pointed out by the Food and Drug Administration, and manifested as a black box on the antidepressant package. One of the most frequent paediatric behavioural disorders is ADHD, whose therapy has been achieved since 1950 employing the stimulants, methylphenidate and amphetamines. The mechanism of action of these drugs, which increase dopaminergic and noradrenergic transmission in selected brain areas, explain their ability to improve significantly ADHD symptoms, like inattentivity, impulsivity, hyperactivity. Because of stimulant-induced side effects, a new drug is now available, with a different pharmacodynamic profile: atomoxetine. This compound, able to selectively inhibit noradrenalin reuptake is as efficacious as psychostimulants, but more tolerated and devoid of rebound effect and risk of addiction. In conclusion, psychotropic drug therapy during childhood and adolescence, except that for stimulants, represent a "learning by doing" work. Nevertheless, the past 10 years have witnessed an intensified effort in research in pediatric psychopharmacology, in order to properly consider domain of function, severity of impairment interval, change or partial improvement. Hopefully, researchers, clinicians and families working together will find a creative balance between therapeutic optimism and appropriate concern about safety of medications with a potential impact on the developing brain.