Journal of E-Technology Indrawati Indrawati, Maya Ariyanti 6 2 2015 http://www.dline.info/jet/fulltext/v6n2/v6n2_1.pdf In Indonesia, the percentage of application downloaded is the second highest in South East Asia after Philippines, but the usage frequency is the lowest (40 minutes) among other countries. In Malaysia, the percentage of application downloaded is the lowest among comparing countries, but the usage frequency is the highest (66 minutes) among other countries. It is important to increase the usage of the application especially in Indonesia which is considered still low compare to Malaysia. In order to increase the usage, factors that influence the behavioral intention and use behavior of people to use the application is important to identify. The objective of this research are to identify and compare factors that affect the behavioral intention and usage behaviour toward instant messenger applications of Indonesians and Malaysian Customers. To acheive the objectives this research had done literature review of published articles which are mainly from international journal and interview and focus group dicussion in several cities in Indonesia with 97 customers and in Malaysia with 36 customers. The result of this process suggest that there are two new variables that should be added to the original UTAUT2 model, namely: interoperability and mobile friendlyness. Thus, this study proposed Performance Expectancy, Effort Expectancy, Social Influence, Facilitating condition, Hedonic Motivation, Price Value, Mobile Friendlyness, and Interoperability as dependent variables which will infuence the behavioural intention and use behavior of customers in Indonesia and Malaysia toward instant messenger applications. Age and gender as moderating variables.