The extended psychosis phenotype, or the expression of non-clinical positive psychotic experiences, is already prevalent in adolescence, and has a dose-response risk relationship with later psychotic disorder. In two large adolescent general population samples (n=5422 and n=2230), prevalence and structure of the extended psychosis phenotype was investigated. Positive psychotic experiences, broadly defined, were reported by the majority of adolescents. Exploratory analysis with Structural Equation Modelling (Exploratory Factor analysis followed by Confirmatory Factor Analysis) in Sample 1 suggested that psychotic experiences were best represented by five underlying dimensions; Confirmatory Factor Analysis in Sample 2 provided a replication of this model. Dimensions were labeled Hallucinations, Delusions, Paranoia, Grandiosity and Paranormal Beliefs. Prevalences differed strongly, Hallucinations having the lowest and Paranoia having the highest rates. Girls reported more experiences on all dimensions, except Grandiosity, and from age 12 to 16 years rates increased. Hallucinations, Delusions and Paranoia, but not Grandiosity and Paranormal beliefs, were associated with distress and general measures of psychopathology. Thus, only some of the dimensions of the extended psychosis phenotype in young people may represent a continuum with more severe psychopathology and predict later psychiatric disorder.