Osteoporosis, a skeletal disorder characterized by compromised bone strength and an increased risk of fractures, is an important paediatric disorder that involves almost all paediatric subspecialties. Osteogenesis imperfecta is the most common form of childhood-onset primary osteoporosis, but several other forms are also known. Secondary osteoporosis is caused by an underlying chronic illness or its treatment. The most common causes of secondary osteoporosis include chronic systemic inflammation, glucocorticoid use and neuromuscular disabilities. The skeletal sequelae can present in childhood as low-energy peripheral and vertebral fractures, or become evident in adulthood as low bone mass and an increased propensity to develop osteoporosis. Management should aim at prevention, as interventions to treat symptomatic osteoporosis in the paediatric age group are scarce. Bisphosphonates are the principal pharmacological agents that can be used in this setting, but data on their efficacy and safety in paediatric populations remain inadequate, especially in patients with secondary osteoporosis. Consequently, it is important to understand the potential skeletal effects of paediatric illnesses and their therapies in order to institute effective and timely prevention of skeletal complications.