The study consists of two parts. Part 1 is an open-label single-dose, non-fasting, multicenter study to evaluate the pharmacokinetics (PK) of paricalcitol capsules in 12 children ages 10 to 16 years with CKD Stages 3 and 4. Part 2 of this study will be conducted as a 12 week randomized double-blind, placebo-controlled study, followed by 12 weeks open-label treatment. Participants active or enrolled under amendment 5 will enter a follow-up period and have study visits every 4 weeks until the final participant reaches Week 24.