Introduction and objective: Asthma is one of the most common chronic diseases in the paediatric population. The aim of this study was to evaluate selected biomarkers: fractional exhaled nitric oxide (FeNO), eosinophil count, periostin; and potential biomarkers: progranulin, matrix metalloproteinase-9 (MMP-9) and tumour necrosis factor alpha (TNFα) in the diagnosis of asthma in children. Materials and methods: The study group consisted of 25 children with atopic asthma in a stable period of the disease, aged 6–17 years. The control group consisted of 21 healthy children aged 6–18 years with no history of allergic diseases. Results: Significantly higher serum periostin levels were observed in children with asthma compared to the control group. There were no statistically significant differences in progranulin, periostin and MMP-9 levels between asthmatic children vs. healthy controls, or between patients with controlled vs. uncontrolled asthma. Children with uncontrolled asthma had significantly higher FeNO levels compared to children with controlled asthma. Exhaled FeNO levels were significantly higher in children with eosinophil levels above 0.3 × 10³/μL than in those with eosinophil levels below 0.3 × 10³/μL. Children with elevated FeNO had higher progranulin levels compared to children with normal FeNO values. There was a statistically significant positive correlation between FeNO and serum progranulin levels. Conclusions: Periostin may be used as a biomarker of atopic asthma in children. The applicability of FeNO and eosinophil count in the diagnosis of asthma in children has been confirmed. The role of progranulin and MMP-9 in the pathogenesis of asthma and their usefulness as a biomarker in children requires further study.