Abstract: Drug-naive and drug-free schizophrenic PBL were screened to identify additional markers that are differentially expressed compared to healthy individuals using microarray and quantitative real-time PCR (QRT-PCR) techniques. Genes for dopamine D2 receptor (DRD2) and inwardly rectifying potassium channel (Kir2.3) were found to be overexpressed in microarray analysis. Increased mRNA levels were confirmed by QRT-PCR using SybrGreen method and dual labeled TaqMan probes. The invention relates to a method for diagnosing schizophrenia in a subject comprising assessing the level or the expression level of at least one of the following genes or proteins: Kir2.3 or DRD2 or a gene encoding Kir2.3 or DRD2. The invention further relates to agents and uses thereof, said agents specifically binding to said proteins or nucleic acids encoding them, diagnostic kits and screening methods.