Children born or living in a familiar environment where illicit drugs are commonly used are exposed to severe health and social risk. The detection of drugs in children biofluids can indicate in utero exposure, systemic ingestion from mother's breast milk, passive or active exposure from caregivers. Hair analysis of children and their relatives is useful to estimate the exposure risk and may be useful in child neglect/child protection cases when contact with drugs of abuse is questioned. The aim of this study is to present and analyze the prevalence and the concentration of illicit drugs in hair samples of children with clinical signs or circumstantial stories of drug exposure, and in hair from their relatives. A retrospective observational study was performed on the hair samples collected in an obstetrician department at the moment of baby delivery, in cases of suspected prenatal drug exposure, and in a paediatric emergency department in cases of children exhibiting symptoms/signs of intoxication or child abuse. Hair samples were analysed at the local forensic toxicology laboratory. Hair samples of children (< 14 years old) and their relatives were collected. After washing, pulverization and solid phase extraction, samples were analyzed by high performance liquid chromatography – high-resolution mass spectrometry, screening for a wide class of psychotropic substances, including cocaine, opiates, opioids, amphetamines and amphetamine-like substances, cathinone and synthetic cathinones, cannabinoids, benzodiazepines, ketamine, Z-drugs. In 100 cases of suspected exposure to drugs, hair from children and their relatives were collected. Prevalence of children with hair positive for illicit drugs was 72%. Hair samples of mothers were collected in 66% of positive cases, with a concordance with child for most of drugs. Hair samples of other relatives were collected in 43% of positive cases. The most frequently detected drugs were cocaine, opiates and opioids, followed by cannabinoids, ketamine and amphetamine-like substances. According to the children age and the match with the drugs detected in the mother hair samples, the main part of cases can be referred to in utero or short-term exposure from the mother's breast milk, while cases due to exposure or ingestion in the family environment are fewer in the selected setting. The concentration of drugs and metabolites were higher in younger children than in their older siblings. Hair analysis is useful for the early identification of child exposure to illicit drugs, to estimate the risk of child neglect in families, and to monitor the outcome of social service interventions.