Nowadays, the issue of stakeholders' effective decision-making has become increasingly important. In most cases the information, provided in financial statements, is not sufficient to make decisions, thus the importance of voluntarily disclosed information increases. The Internet and companies' websites may serve as a vehicle for the provision of such information. Therefore, the purpose of the article is to measure the extent of voluntary information disclosure on the websites of Lithuanian companies and to investigate whether there is a significant association between theoretically possible disclosure determinants. Research methods used in the study are the following: comparative analysis of scientific literature, logical, systematic analysis, content analysis using scope and quantity index approaches and correlation analysis using Spearman's rank correlation coefficient. Results showed a statistically significant connection between the company's size (as determined by its earnings) and the company's voluntary information disclosure index. The companies with higher earnings are inclined to provide a wider scope and a larger volume of information. Furthermore, the connection between the number of employees and the word quantity index wasn't established. This research adds to the samples of previous studies and analyses disclosure of financial and non-financial information on companies' websites.