Parkinson's disease (PD) has been described as an age-related disease. Ageing significantly increases the risk of psychosis and dementia. Older patients often have a complex mixture of delirium, psychosis, dementia, gait and balance problems and other comorbidities which can cause significant management problems. There are concerns about the safety and tolerability of the treatments for psychosis and dementia. Delirium is common in older Parkinson's patients and must be assessed and managed carefully. The aetiology of psychosis in Parkinson's is complex and often associated with the development of cognitive impairment. Initial adjustments of Parkinson's drugs should be considered if symptoms are intrusive. Where drug therapy is required, evidence suggests that quetiapine may be a safe initial option. There is no contraindication to the use of clozapine in older patients, with the required blood monitoring. Dementia is almost inevitable with very advanced disease and increasing age, and is associated with a marked cholinergic deficit in the brain. Cholinesterase inhibitors may be more effective in PD than in Alzheimer's disease and appear relatively safe with appropriate monitoring of the pulse. There is much less evidence for the use of memantine. There is no current evidence for the use of specific non-pharmacological therapies in the management of psychosis or dementia in PD. Due to the associated gait and balance problems, older Parkinson's patients benefit from comprehensive multi-disciplinary assessment.