Although circulating microRNAs (miRNAs) were frequently detected in sera of cancer patients, there is still a lack of analysis of the dynamic changes of miRNAs expression in sera of pre- and post-operative lung carcinoma patients. Thus, we conducted quantitative reverse transcription-polymerase chain reaction (qRT-PCR) to examine the expression of four miRNAs (miR-21, miR-205, miR-30d, and miR-24) in the sera of a set of 82 pre-operative lung carcinoma patients and paired 10 days post-operative patients, as well as in 50 normal volunteers. We showed that, compared to that in normal volunteers, the expression of miR-21, miR-205, miR-30d, and miR-24 was increased in lung cancer sera samples, as well as in sera of early stage lung cancer patients according to their clinical-pathological characteristics. The area under roc curves (AUCs) for levels of miR-21, miR-205, miR-30d, and miR-24 in sera were significantly higher than those for Carcinoma embryonic antigen (CEA) (P < 0.05), whereas the AUC for combination of serum levels of miRNA with serum CEA showed no significant difference from that for serum levels of miRNAs only (P > 0.05). The expression levels of miR-21 and miR-24 were significantly decreased in post-operative sera compared with levels in paired pre-operative sera (P = 0.0004 and <0.0001, respectively). In addition, high expressions of miR-21 and miR-30d in pre-operative sera were independently correlated with shorter overall survival in lung cancer patients (log-rank test: P = 0.0498, 0.0019). In summary, our results suggest that miR-21, miR-205, miR-30d, and miR-24 may serve as potential novel non-invasive biomarkers for diagnosis of lung cancer. In addition, miR-21 and miR-24 serum levels were lower in post-operative samples than those in pre-operative samples, suggesting they can potentially be used as biomarkers for disease recurrence after surgery operation.