Altered promoter activity has been generally observed in diverse biological processes, including tumorigenesis. Accumulating evidence suggests that employing a quantitative trait locus mapping approach is effective in comprehending the genetic basis of promoter activity. By utilizing genot ype dat a from The Cancer Genome Atlas and calculating corresponding promoter activity v alues using proA ctiv, w e sy stematically e v aluated the impact of genetic variants on promoter activity and identified > 1.0 million promoter activity quantitative trait loci (paQTLs) as both cis-and trans-acting. A dditionally, le v eraging data from the genome-wide association study (GWAS) cat alog , w e disco v ered > 1.3 million paQTLs that o v erlap with kno wn GWAS linkage disequilibrium regions. R emarkably, similar to 9324 paQTLs e xhibited significant associations with patient prognosis. Moreo v er, in v estigating the impact of promoter activity on > 10 0 0 imputed antitumor therapy responses among pan-cancer patients re v ealed > 43 0 0 0 million significant associations. Furthermore, similar to 25 0 0 0 significant associations were identified bet ween promoter activit y and immune cell abundance. Finally, a user-friendly dat a port al, Pancan-paQTL ( https://www.hbpding .com/P ancanP aQTL/), w as constructed f or users to browse, search and download data of interest. Pancan-paQTL serves as a comprehensive multidimensional database, enabling functional and clinical in v estigations into genetic v ariants associated with promoter activity, drug responses and immune infiltration across multiple cancer types. [GRAPHICS]