This chapter deals with smartphone addiction in children and adolescents. Smartphone addiction appears to be the latest behavioral addiction to emerge. The chapter describes the prevalence and risk factors of smartphone addiction. The risk factors are sociodemographic factors such as young age, psychological traits such as stress, loneliness, depression, or anxiety, and familial factors. The chapter discusses the consequences of smartphone addiction. Smartphone addiction affects one’s physical, psychological, and social well-being. Physical health consequences are motor vehicle crash, musculoskeletal disorders, eye and visual symptoms such as ocular discomfort, eyestrain, dry eye, headache, blurred vision, and double vision, electromagnetic radiation, and infection. Mental health consequence is sleep disturbance. Nomophobia, an abbreviation for no-mobile-phone phobia, phantom vibration syndrome, and ringxiety are some new terminologies about distress one receives because of excessive smartphone usage. Smartphone addiction also affects social interactions and academic performance.