OBJECTIVES: Mental and behavioural disorders contributed 12.9% of the total burden of disease in Australia, and pharmaceuticals are recommended as treatment for people with moderate to severe conditions. The aim of this research was to estimate the costs of pharmaceuticals to the Australian public health sector and the most frequently prescribed drugs for the three most prevalent mental illnesses: depression, anxiety-related, and substance use disorders. METHODS: The National Survey of Mental Health and Wellbeing(NSMHWB) has been conducted every 10 years since 1997, collecting epidemiology and  economic impact to Australian society. Respondents diagnosed within the preceding 12 months with depression (D), anxiety-related disorders (ANX), and substance use disorders (SUB) by ICD-10 in NSMHWB 2007 were included in the analysis. The NSMHWB 2007 reported the duration and the name of up to five drugs used during the past 12-month period. In order to adjust for inflation, 2013-14 reference year was adopted for the unit cost of each drug obtained from Pharmaceutical Benefit Scheme (PBS). RESULTS: Around 23% of respondents used medications for a total cost to the society of AUD 101 million (SE 11.9). Citalopram was the most frequently prescribed drug (17.11%), followed by venlafaxine (15.65%), sertraline (14.43%), and temazepam (10.51%). Respondents reported with D+ANX+SUB had the highest percentage in use of medications (63.85%), followed by D+ANX (44.26%), and D (34.74%). ANX accounted for 50% of total medication costs followed by D+ANX at 23.6%. CONCLUSIONS: The high prevalence of ANX contributed to the large proportion of medication costs for this condition.