We report patterns of hospitalization in schizophrenic psychoses by age 34 in a longitudinal population-based cohort. We test the predictive ability of various demographic and illness-related variables on patterns of hospitalization, with a special focus on the length of the first psychiatric hospitalization. All living subjects of the Northern Finland 1966 Birth Cohort with DSM-III-R schizophrenia (n=88) and other schizophrenia spectrum cases (n=27) by the year 1997 in the Finnish Hospital Discharge Register were followed for an average of 10.5 years. Measures of psychiatric hospitalization included time to re-hospitalization (as continuous and as re-hospitalization within 2 years) and the number of hospital episodes. Length of the first hospitalization, other illness-related and various socio-demographic predictors were used to predict hospitalization patterns. After adjusting for gender, age at first admission and number of hospital days a short (1-14 days) first hospitalization (reference >30 days; adjusted odds ratio 6.39; 95% CI 2.00-20.41) and familial risk of psychosis (OR 3.36; 1.09-10.39) predicted re-hospitalization within 2 years. A short first hospitalization also predicted frequent psychiatric admissions defined as the first three admissions within 3 years (OR 13.77; 3.92-48.36). A short first hospitalization was linked to increased risk of re-hospitalizations. Although short hospitalization is recommended by several guidelines, there may be a group of patients with schizophrenic psychoses in which too short a hospitalization may lead to inadequate treatment response.