During the last decades, the number of patients with long stay admissions (LSA) in PICU has increased. The purpose of this study was to identify factors associated with PICU LSA, assessing healthcare resources use and changes in the profile of these patients. A retrospective, observational, single-center study was carried out. Characteristics of LSA were compared between two periods (2006-2010 and 2011-2015). During the earlier period there were 2,118 admissions (3.9% of them LSA), whereas during the second period, there were 1,763 (5.4% of them LSA) (p = 0.025). LSA accounted for 33.7% PICU stay days during the first period and 46.7% during the second (p < 0.001). Higher use of non-invasive ventilation (80.2% vs. 37.8%, p = 0.001) and high-flow oxygen therapy (68.8% vs. 37.8%, p = 0.005) was observed in the 2011-2015 cohort, whereas the use of arterial catheter (77.1% vs. 92.6%, p = 0.005), continuous infusion of adrenaline (55.2% vs. 75.9%, p = 0.004), and hemoderivative transfusion (74% vs. 89.2%, p = 0.010) was less frequent. In the 2006-2010 cohort, hospital-acquired infections were more common (95.2% vs. 68.8%, p < 0.001) and mortality was higher (26.8% vs. 13.8%, p = 0.026). The number of long-stay PICU admissions have increased entailing an intensive use of healthcare resources. These patients have a high risk for complications and mortality.