Introduction: In 2020, the World Health Organization-International Agency for Research on Cancer/International Academy of Cytology (WHO-IARC IAC) joint project was commenced to develop standardized nomenclature and diagnostic criteria in cytopathology internationally. Our institution has been coding all respiratory cytological specimens in a similar fashion for over 10 years. Our aim was to analyse the effectiveness of our respiratory cytology coding system by calculating the estimated risk of malignancy (ROM) and rates of each diagnostic category. Methods: Over a 2 year period, all endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA), bronchial brushing, bronchial washing, bronchial lavage, and sputum specimens reported at our institution were analysed. For each specimen, the diagnostic code, the relevant indication for each diagnostic procedure, the diagnosis, and the presence or absence of a positive corresponding biopsy were recorded. Results: In total, 1,432 respiratory cytological specimens from 945 patients over a 2-year period were analysed. 467 specimens were confirmed to be associated with a malignant process. The overall ROM for respiratory cytology specimens was 37.7% for nondiagnostic, 18.1% for benign, 46.7% for atypical, 85.7% for suspicious for malignancy, and 91.9% for malignant. For each diagnostic procedure, the ROM increased from the benign to malignant categories. Discussion/Conclusion: Our ROM rates for overall respiratory cytology specimens and for EBUS-TBNA, bronchial brushing, and bronchial washing specimens separately are concordant with other major international studies. With the WHO-IARC IAC joint project in progress and an international respiratory cytology coding system being developed, our study has the potential to add value by providing indicative ROM rates, which can be used to inform the development of this new classification system. Our rates of diagnostic accuracy are in keeping with international standards, which support the accuracy of our data.