<b><i>Objectives:</i></b> Cytological analysis of peripheral blood circulating tumour cells (CTCs) is a potential method of confirmatory clinical diagnosis of cancer. However, cell capture methods tend to be biased and captured cells are not usually portable resulting in difficulties in pathology reporting. We evaluated unbiased cell capture through depletion of unwanted normal cells and conventional clinical analyses of captured cells. <b><i>Methods:</i></b> Blood was sampled from 29 patients who underwent surgery for suspected lung cancer. It was processed using two different depletion cocktails. After depletion of unwanted cells, the resultant cell pellet was processed onto glass slides or embedded into FFPE blocks and stained using standard haematoxylin and eosin staining followed by cytopathologic assessment. Two pathologists performed the assessment independently. <b><i>Results:</i></b> The CTCs were identified in 38-45% of cases using CD45 depletion cocktail with the cell pellet processed on a glass slide, while other combinations of methods produced poorer results. Overall, there was a good concordance between the pathologists (up to 91.3%). The sensitivity of cancer diagnosis was 42% (95% CI 23-63%), while the specificity was 100% (95% CI 29-100%). <b><i>Conclusion:</i></b> Negative depletion can be used to isolate CTCs in standard clinical settings; however, more effective ways of detection are required to increase the sensitivity of the diagnosis.