The Brain cytoplasmic 200 RNA (BC200 RNA) is neuron-specific lncRNA with putative roles in normal aging and in the pathogenesis of Alzheimer’s disease. Its role in the neuron plasticity has also been documented. In the current study, we genotyped a single nucleotide polymorphism (SNP) within this lncRNA (rs4404327) in a population of Iranian patients with diverse neuropsychiatric conditions including substance addiction (n = 315), attention deficit hyperactive disorder (ADHD) (n = 53), bipolar 1 (BP1) (n = 131), bipolar 2 (BP2) (n = 68), major depressive disorder (MDD) (n = 56) and schizophrenia (SCZ) (n = 177) as well as age-/ sex-matched healthy controls. This SNP was associated with ADHD in co-dominant model (C/T vs. C/C) (OR (95% CI) = 3.7 (1.96-10), P value = 0.000193), dominant model (C/T + T/T vs. C/C) (OR (95% CI) = 4.43(2.02-9.72), P value = 1.37E-04) and multiplicative model (C vs. T) (OR (95% CI) = 3.20(1.64-6.25), P value = 4.316269E-04). Moreover, this SNP was associated with risk of BP1 in dominant model (OR (95% CI) = 1.67(1.08-2.62), P value = 0.02) and multiplicative model (OR (95% CI) = 1.51 (1.04-2.21), P value = 0.028). After correction for multiple comparisons (6 cohorts × 4 models), associations remained significant in ADHD but not in BP1. No other significant association was detected. The current project showed association between a certain SNP within BC200 RNA and ADHD. Further studies are required to assess these associations in larger cohorts of patients and find the underlying mechanism for this observation.