To examine the adequacy of samples and accuracy of transthoracic needle aspiration (TTNA) in patients with peripheral pulmonary nodule (PPN) diagnosis. This retrospective study included 248 patients who underwent TTNA of PPN and subsequent diagnostic and therapeutic surgical procedures during a 5-year period at the Institute for Pulmonary Diseases of Vojvodina. The following were analysed: adequacy of cytological samples for diagnosis and molecular testing, tumour localisation and dimensions, and cytological and histopathological characteristics. The adequacy of the cytological samples was 93.15%. The proportion of adequate-diagnostic samples was higher in patients in whom the largest diameter of the lesion was >4cm, and this difference showed statistical significance. Tumour localisation was not statistically significant for the adequacy of samples for cytological analysis. Cytological samples of lung adenocarcinoma had high projected adequacy for EGFR analyses of 91.55%, not dependent on the size and location of the lesion. The most commonly diagnosed lung tumour was adenocarcinoma (45.51%). Patients with a cytological diagnosis of non-small cell carcinoma not otherwise specified, after histopathological analyses, had adenocarcinoma in most cases (53.85%). The overall accuracy of TTNA in the diagnosis of PPN was 71%. The method's accuracy was 75.24% for malignant tumours, while it was 28.57% for benign tumours. The accuracy of cytological analysis for the histological type of tumour was 84.18%. Transthoracic needle aspiration with cytological analysis is an effective and highly sensitive method in determining the aetiology of PPN.