BACKGROUND: Chronic gastritis is a common histologic finding in children with functional dyspepsia (FD). While Th17 cells have been implicated in other forms of gastritis, they have not been evaluated in chronic gastritis. AIMS: The aim of the current study was to assess Th17 cells in children with FD with and without chronic gastritis. METHODS: Densities were determined for Th17 cells, eosinophils, and mast cells, respectively, in both the gastric antrum and the duodenum. Densities were compared between five groups: FD with chronic gastritis (N = 20), FD without chronic gastritis (N = 20), Helicobacter pylori-associated gastritis (N = 10), Crohn's gastritis (N = 10), and normal controls (N = 10). Th17 densities were also compared between patients with and without early satiety. RESULTS: FD with chronic gastritis was associated with higher Th17 cell density as compared to normal controls and comparable to both H. pylori-associated gastritis and Crohn's gastritis. Eosinophil and mast cell densities were higher in FD patients with chronic gastritis as compared to either FD without gastritis or normal controls. Th17 density was higher in patients reporting early satiety but not in those with epigastric pain. CONCLUSIONS: FD with chronic gastritis is associated with higher Th17 cell, eosinophil, and mast cell density as compared to FD without chronic gastritis or normal controls. Chronic gastritis demonstrated Th17 cell density similar to that seen in other conditions where Th17 cells are believed to play a pathogenic role. Th17 cells may represent another therapeutic target in these patients.