There are an increasing number of companies in the mining and metals sector disclosing environmental sustainability information in their annual reports, sustainability reports and corporate internet web pages. However, there is ongoing debate about the relationship between the quantity and the quality of environmental disclosure. That is, does an increase in number equate to an increase in quality? This study investigates the relationship between the quantity and the quality of environmental disclosure reports. Using content analysis, we examine the environmental disclosure of 55 Australian mining and metal companies which are listed among the Australian Securities Exchange's (ASX) Top 100 mining and metal sector companies. We find that the size of firms influences both the quantity and the quality of corporate environmental disclosure. That is, we find that market capitalization is positively and significantly correlated to the quantity (number of words) and the quality of disclosure. We also confirm that there is a very highly significant, positive correlation between quantity (number of words) and quality of environmental disclosure. In order to investigate any differences between the top performing group and the bottom performing group in terms of environmental disclosure quality, further analysis also confirms that there is a positive relationship between the quantity and the quality of environmental disclosure. Copyright © 2015 John Wiley & Sons, Ltd and ERP Environment