Juvenile court erred when it terminated dependency jurisdiction over an 18-year-old dependent who was returned to her mother’s custody but then abandoned by mother. Shannon was returned to her mother’s care just before her 18th birthday and abandoned by her mother shortly after she turned 18. The Department asked the court to terminate dependency jurisdiction. Shannon objected, contending that the court had to first consider whether that was in her best interest. The juvenile court terminated dependency, and the appellate court reversed. The juvenile court erred in relying on section 364, which governs the termination of jurisdiction after a dependent has been placed with the parent. Regardless of where the dependent is placed, section 391 governs the termination of jurisdiction based on a dependent reaching the age of majority. Under section 391, the court cannot terminate its jurisdiction without holding a hearing to determine whether that action would be in the nonminor’s best interest. Here, there was insufficient evidence the court considered Shannon’s best interests.