Adolescents between 13 -18 years form the highest age group regarding internet penetration in Indonesia. As a digital native, they have the skills to use those technologies. They live in a digitalized world; so many aspects of their life are spent online, in particular human relationships. For them, computers and smartphone are primary mediators of human to human interactions. As smartphone play a role as the hardware, social media act as its primary software in establishing social relation. The use of smartphones and social media helps many aspects of adolescent life but also have many negatives impact. Internet addiction has become one of the most serious issues, of which depression is most frequently reported. The purpose of this study is to find out adolescents’ behavior in using the smartphone and also what they do in social media as an early effort to prevent the adverse effects of smartphone and social media.

5039 junior high school students in the city of Bandung (2322 men, 2640 women) from 28 junior high schools and madrasah obtained using cluster sampling. The majority of ages 13-14 years (1002 aged 12 years old, 1769 aged 13 years, 1636 aged 14 years), given questions related to behavior using smartphone and social media through self-administered questionnaires.

88.6% of respondents own a smartphone and 83.3% of them are having a smartphone that always connected to the internet. The majority of respondents use smartphones 3 - 4 hours a day. For them, having a smartphone make them easier to connect with friends, facilitate them to get information that adds skills and they can listen to music anytime they want. The main activity they do with smartphone is to receive and send messages via whatsapp / line, search for information and play online games. In relation to social media, 94% of respondents have social media. Most of the respondents are using Instagram, Line, and Facebook. Activities they often do in social media are chatting, giving "like" to friends / people posts, and posting photos with friends.

Smartphone and social media have become a part of adolescent life. Adolescent are more likely to feel the positive impact of using smartphone and social media in their lives especially in social relationships. Many of their activities they do on smartphone and social media support their social life. The types of social media they have are social networking systems that allow them to build social identities within the bounded systems that they create themselves by actively selecting anyone whom they want share a connection. Adolescents practice their social skills through chatting, learn to establishing and maintaining friendships by giving “like” to friends / people post and posting their photos with friends and even to seek social identity.

Indonesians’ adolescent still need guidance in adapting to the digital world. But, research related to adolescent and mobile phone or social media has not been much in Indonesia. The results of this study can be a useful input to develop guidance for adolescent in using gadgets and social media.