The purpose of this study is to monitor the long-term safety of ustekinumab in pediatric participants (aged greater than or equal to 12 years to less than 18 years inclusive) with moderate to severe plaque psoriasis, through monitoring for the following adverse events potentially related to immune modulation: serious infections, malignancies and autoimmunity; and to monitor the long-term effects of ustekinumab on growth (weight, height, body mass index) and development (sexual maturity based on the Tanner Scale).