Despite the recognized benefits of organized cancer screening programs, tests outside screening programs are common. Downsides to this practice include the lack of quality control and disparities in participation patterns based on one’s perception of risk and willingness/ability to pay. While comprehensive reports on outside program screening in Europe are lacking, the Flemish breast (BC) and colorectal cancer (CRC) screening programs monitor data on non-organized tests prescribed by GPs and specialists. Using multivariate logistic regression, we examined the relationship between health care utilization and BC and CRC screening coverage in 308 Flemish municipalities between 2015–2018. With regards to BC, municipalities with a higher rate of visits with gynecologists have a lower coverage inside (-8%) and higher coverage outside (+17%) the program. By contrast, municipalities with a higher rate of GP visits, have a higher coverage inside (6%) and a lower coverage outside (-7%) the program. As for CRC, municipalities with a higher rate of visits with gastroenterologists have a lower coverage inside the program (-3%). Instead, municipalities with a higher rate of GP visits, have a higher coverage both inside (+2%) and outside (+5%) the program. Municipalities with a higher percentage of people with chronic conditions have a higher coverage within both the BC and CRC programs (+5% and +3%), and lower rates of outside screening (-7% and -6%). Municipalities with a higher percentage of people 65+ affected by dementia, partially overlapping with the target population, have higher inside coverage in both the BC and CRC screening (+13% and +5%, respectively). Finally, a higher percentage of people with mood disorders was associated with lower inside coverage of BC and CRC screening (-3% and -4%). Providers should remain aware of their role in facilitating patients’ decision-making process, especially among vulnerable groups, and attempt to increase participation in the organized programs.