Background: People with learning disability (LD) experience a range of mental health problems. They are a complex population, whose needs are not well understood. This study focuses on the development of a systematic process of needs assessment for this population. Methods: The Cardinal Needs Schedule used in general psychiatry was adapted for people with learning disabilities (LD). The Learning Disability version of the Cardinal Needs Schedule (LDCNS) was tested on a sample of 35 people with LD and mental illness for its inter-rater reliability. Results: The inter-rater reliability (Kappa) was calculated for 22 areas of functioning assessed by the LDCNS. Overall, there was very good agreement in seven areas, moderate agreement in six areas, fair agreement in three areas and poor agreement in one area. In four areas of functioning, Kappa could not be calculated. More needs were found in the social domain than in the clinical domain. Conclusion: A systematic needs assessment schedule (LDCNS) was developed for people with LD and mental illness. The inter-rater reliability is generally acceptable, but requires further examination.