Background: Approximately 2-3% of lung cancer (LC) was found in very young patients (≤ 45 years old) and they were reported to have different clinical characteristics and genetic profiles when compared to older patients. However, it is still lack of large-scale genomic studies that could provide deep insights into the tumorigenesis, precision treatment and prognosis for this particular population. Methods: Clinically annotated data of targeted next generation sequencing (NGS) on 7858 tumor tissue specimens from LC patients were analyzed. For all specimens, a total of 422 or 425 cancer-related genes were interrogated with a mean coverage depth greater than 500x. Results: Of 7858 LC cases, 814 of them were younger than 45 (age at diagnosis), which were compared to 7044 old LC cases ( > 45 years old). Clinical information showed that young LC are more prevalent in female, to be more advanced disease and to have more adenocarcinoma in histology. Somatic genomic data analysis revealed that compared to old LC, young LC has significantly higher ALK/ROS1/RET fusions, ERBB2 mutations and 5q amplification(FDR < 0.1), but lower mutational frequencies in KRAS, CDKN2A, ERBB4, FAT1, NF1, lower copy number gain (CNG) of PIK3CA, MDM2, FGFR1, and less 5q deletion(FDR < 0.1). Interestingly, in young LC, genetic differences between female and male are not significant, with TP53 and EGFR being most frequently mutated in both sexes. Similarly, the differences between young and old female LC are also limit, with young female LC having more ALK fusions (13.43% vs. 5.1%, FDR < 0.01), less EGFR mutations and MDM2 CNG than old female. On the contrary, male patients demonstrated much wide disparity between young and old LC: young LC was enriched with ALK/ROS1/RET/ERBB2 fusions and mutations in EGFR, ERBB2 and SMAD2, while old LC have more mutations in KRAS, TP53, CDKN2A, and CNG of PIK3CA (all FDR < 0.1). We also found that EGFR exon19 deletion (19del) was significantly enriched in young LC, especially in male, while p.L858R showed preference in old LC. Conclusions: The data suggest that the prevalence of different genetic alterations is both age and sex related. The high level of ALK/ROS1/RET fusions and less CNV in young LC could potentially lead to more effective treatment and better prognosis. We also noted that genomic alterations in young LC were not significantly different across sexes, but the disparity by sex was enormously enlarged in old LC, which might be correlated to their life-long exposures, such as smoking, life styles and sex-affected factors.