Diagnostic methods for detection of Helicobacter pylori may be classified as invasive, i.e. requiring endoscopy and specimens from the gastric mucosa, and noninvasive. Invasive methods detect bacteria or bacterial urease in a specimen of the gastric mucosa. Noninvasive tests as ¹³,¹⁴C urea breath test is based on urease production of bacteria, while stool antigen test detects bacteria and is suited to detect active infection. Serology allows to detect Helicobacter pyloriantibodies and shows contact with the helicobacter. In children and young adults urea breath test and stool antigen test are first-line tests before endoscopy. Pretreatment diagnostic tests are endoscopy and biopsy from the gastric mucosa, urea breath test, stool antigen test and serology. Posttreatment tests are stool antigen test, urea breath test and in selected cases serology. Testing of Helicobacter pylori is always connected with agreement to undergo triple therapy in the care of positive test results.