Office workers spend a lot of time in front of screens at the workplace and at home. Nowadays the smartphone is the most used device, and it is not clear how it can affect our health and wellbeing. Consequently, the objective of this research was to analyse the relationship between smartphone use and body composition (BC), physical fitness (PF), quality of life (QoL) and selective attention (SA) in office workers. A cross-sectional pilot study was carried out with 30 office workers (16 men and 14 women) who were between 27 and 59 years old. We collected their BC (height, weight, body mass index, waist-hip ratio -WHR-and fat mass percentage), PF (countermovement jump -CMJ-, handgrip strength and cardiovascular endurance performing the 6-min walk test), QoL (SF-36), SA (Stroop Test) and smartphone use. As a result, smartphone use was significantly correlated with QoL dimensions, pain (r 2 = 0.219, p = 0.04) and physical component (r 2 = 0.153, p = 0.03). Smartphone use was also correlated with the congruent score (r 2 = 0.143, p = 0.01) and the "Stroop Effect" (r 2 = 0.195, p < 0.01). The results of this pilot study suggest that smartphone use could correlate with QoL dimensions and SA. It will be necessary to continue and expand the study to acquire more knowledge about how these devices affect health and wellbeing.