The rise of new communication technologies such as instant messaging systems in enterprises enables employees to communicate and cooperate in new ways. In general, it is believed that these new communication technologies have a positive impact on communication effectiveness and the attitude towards information sharing of employees but at the same time some negative impacts as well, such as creating communication and information overload for the individual. However, how these technologies really change the communication behaviour is still not well understood, wherefore we conducted an empirical, questionnaire-based survey among the employees of a large multi-national financial institution. Based on the responses of 227 employees, we found that the attitude towards information sharing influences the perceived usefulness of instant messaging systems. Moreover, we found that the information overload has a negative moderating effect on the relation between the attitude towards information sharing among employees and perceived usefulness of the system