This paper investigates the coding of dementia in the episode of care in a pilot study group (N=48) post hospital discharge and the possible implications of under-coding. The assigned ICD-10-AM codes and Diagnosis Related Groups were reviewed. Results demonstrate under-coding of dementia and of cognitive deficits; poor correlation between admission diagnoses and dementia codes on separation; and changes in individual patients' cognitive status across forms and assessments in the same admission. The complexities of accurately coding dementias will impact upon planning for future treatments and service provision and will have a flow-on effect for patients, hospitals, and patient care in Australia.