Treating patients with multiple oral leucoplakias (MOLs) who smoke is more difficult and complicated than treating those with single oral leucoplakia (SOL). Removing the aetiological factors causing MOL can effectively prevent its recurrence. The aim was to study the infection by and influences of Candida in smoking patients with MOLs. A retrospective study was conducted on 136 smoking patients who had clinicopathological OLs. Among these patients, 73 lesions in 31 patients were MOLs, while 105 patients had SOLs. All patients were treated by complete resection. All specimens were tested for epithelial dysplasia, and stained with periodic acid–Schiff reagent. The rate of MOL concurrence with candidal infection was higher than that of SOLs. The incidence of Candida associated with MOLs was higher for recurrent than for non-recurrent lesions. The disease-free time was shorter in MOL patients with candidal infection. Moreover, MOLs with candidal infection were more likely to have an increasing ratio to combine with epithelial dysplasia. Candida is an important risk factor in smoking patients with MOLs. Microscopic and fungal examinations of those lesions should permit a detailed diagnosis in such patients and for long-term predictive assessments.