<strong>Introduction:</strong> Information and Communication Technologies (i.e., ICT) are fundamental in everyone’s daily lives, especially for youths who integrate them into their routines as instruments for academic, relational, and entertainment purposes (Oka et al., 2021). Thus, it becomes crucial to differentiate positive or proactive online behaviors, which motivate people to interact directly with others and are positively associated with well-being, from negative or addictive online behaviors, which increase emotional, behavioral, or work-related and academic problems (Alimoradi et al., 2019; Gjoneska et al., 2022; Oka et al., 2021). Social and clinical policies are mostly focused on negative and addictive online behaviors in youths, due to their huge effects on mental health, which also significantly impact social and health costs to deal with these problems (Cañas &amp; Estévez, 2021; Lopez-Fernandez &amp; Kuss, 2020). To our knowledge, promotive policies and interventions in this field are still lacking, because they mostly focus only on the reduction of problematic behaviors rather than promoting individual or contextual protective factors (Cañas &amp; Estévez, 2021; Li et al., 2020). Contrary to this trend, considering the potentiality of ICTs for youths, research is now highlighting the importance of considering both preventive and promotive components in online behaviors. According to the Positive Youth Development perspective (Lerner et al., 2018), which emphasized the importance of focusing on individuals’ resources and protective factors, a preventive-promotive intervention was developed and implemented in an Italian Junior High School, that aimed to contrast negative online behaviors, while promoting positive ones (La Rose et al., 2010). <strong>Aims of this Study:</strong> Thus, the present study preliminary investigated the effectiveness of this intervention, by analyzing longitudinal mean differences of two negative (i.e., problematic use of social network and smartphones) and two positive (i.e., searching for social support online, offering social support online) internet-related behaviors in youths. <strong>Method and Results:</strong> 358 youths (35% females; Mage=15.35, S.D.=.63) completed the Bergen Social Media Addiction Scale (Monacis et al., 2017), the Smartphone Addiction Scale (Kwon et al., 2013), and the Active and Passive Use of Social Networking Sites Scale (Remondi et al., 2023) in the pre-and-post intervention assessments. Repeated Analysis of Variances showed that smartphone and SNS addictions significantly decreased from pre-to-post assessments. In addition, offering and searching for social support on SN significantly increased across the two time points. <strong>Discussion:</strong> Our findings showed that addictive smartphone and SNS use significantly decreased in a short time period, while relational activities engaged with SNS significantly increased across the intervention. These results could suggest the short-term efficacy of the project and could be considered in the implementation of other school-based interventions, and in the implementation of more effective socioeconomic strategies to contrast internet-related addictive behaviors (Andreassen et al., 2017).