Pulmonary function testing (PFT) techniques are well established in children and adolescents. However, children aged 2-6 years represent a real challenge in pulmonary function assessment as they cannot be sedated and find it difficult to cooperate with all respiratory manoeuvres. In 2007, an ATS and ERS statement on PFT in preschool children summarized the current knowledge on the PFT techniques suitable for young children [65, 66] .