INTRODUCTION: In high-income countries, advances in early diagnosis and treatment have improved cancer survival. However, socioeconomic inequalities in survival have persisted or increased for some adult cancers. MATERIALS AND METHODS: We assessed net survival for the 20 most common adult cancers in Taiwan. They were stratified into six age groups and three socioeconomic groups. RESULTS: Out of 120 cancer site and age group combinations, 49 showed improvements in 5-year net survival from 2000-2004 to 2005-2010. Only cervix uteri cancer in the 35-49-year age group showed a deterioration. During 2000-2010, 13 of the 20 cancer cases experienced socioeconomic inequalities for all age groups combined, and the deprivation gaps varied with cancer site and age at diagnosis. For the five most common cancers - liver, colon and rectum, lung, breast, and oral - there were socioeconomic inequalities, and 5-year net survival improved for most or all of the six age groups from 2000-2004 to 2005-2010. CONCLUSION: Reducing socioeconomic inequality in survival may lead to improvements in survival overall. We should focus on the age groups with large deprivation gaps. Our results are useful for prioritizing cancer sites and age groups for in-depth socioeconomic disparity studies and for proposing interventions for health disparity reductions and net cancer survival improvements.