Attention-Deficit/Hyperactivity Disorder (ADHD), the most prevalent behavioral disorder in childhood, affects 4% of children, affecting social and academic functioning.Methylphenidate (MTPH), a psychostimulant with amphetamine-like properties, is the most prescribed treatment for ADHD.Considering the impact of early substance exposure on later addiction risk, chronic MTPH use during childhood or adolescence may increase vulnerability to substance abuse.Globally, 2 billion people consume or abuse alcohol, accounting for 4% of deaths. We examined the long-term impact of chronic MTPH during childhood/adolescence on ethanol-related behaviors in a validated ADHD mouse model, focusing on voluntary ethanol consumption in adulthood. p35KO transgenic mice and wild-type (WT) controls were treated with MTPH from postnatal days 21–31.In adulthood, we assessed ethanol-induced locomotor stimulation, sensitization, risk-related behaviors, and 24-h voluntary ethanol intake. Early MTPH treatment produced long-lasting, sex- and genotype-dependent effects on ethanol sensitivity.WT mice showed acute locomotor activation, with sensitization only in females, whereas p35KO responded only after 14 days of repeated exposure. MTPH also enhanced impulsive-like behaviors and voluntary ethanol preference and consumption in male WT and female p35KO mice,indicating higher addiction risk.These findings suggest that early psychostimulant exposure may increase alcohol sensitivity and impulsivity in adulthod