Autism is a neurodevelopmental disorder that is often comorbid with seizures. Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in brain. GABAB receptors play an important role in maintaining excitatory-inhibitory balance in brain and alterations may lead to seizures. We compared levels of GABAB receptor subunits GABAB receptor 1 (GABBR1) and GABAB receptor 2 (GABBR2) in cerebellum, Brodmann's area 9 (BA9), and BA40 of subjects with autism and matched controls. Levels of GABBR1 were significantly decreased in BA9, BA40, and cerebellum, while GABBR2 was significantly reduced in the cerebellum. The presence of seizure disorder did not have a significant impact on the observed reductions in GABAB receptor subunit expression. Decreases in GABAB receptor subunits may help explain the presence of seizures that are often comorbid with autism, as well as cognitive difficulties prevalent in autism.