The fact that more and more people are speaking out against drug addiction, respectively on the harmfulness of using drugs for the physical and for the spiritual life, as well as for social cohesion, imposes a general mobilization of law enforcement, medicine and of the Church. The present study aims to show that drug addiction is a behavioural dysfunction and a sin against human nature. For this reason, the study starts from clarifying the notion of drug addiction and the way in which it affects human life on physical, spiritual and social levels. Thus, the initial pleasure gained from using drugs is followed by a morbid phase that ends in degradation and leads to personal collapse. The second part of this study, entitle „A presentation of drug addiction”, analyses the psychoactive substances according to the effect they have on self-awareness, behaviour, and mood, dividing them into several categories, as follows: 1. Sedatives (alcohol, barbiturates, minor tranquilizers; 2. Narcotics or opiates (codeine, heroin, morphine); 3. Psych-stimulants (amphetamines, cocaine, nicotine, caffeine); 4. Hallucinogens (LSD, mescaline, psycholocybin, PCP); 5. Psychoactive (cannabis, marijuana, hashish) and 6. Ethno-botanical substances.