It consists of the part of the city of Vaughan that is east of Highway 400 and south of Rutherford Road, and the part of the city of Markham west of Highway 404.
It is one of only two ridings in Canada with a Jewish plurality (the other being Mount Royal in Quebec). 36.6% of the population is Jewish, the highest in Canada. In addition to religion, Jewish is also the ethnic origin for the plurality of the population, reaching 30.3%, the highest such percentage in Canada. The Thornhill riding also has the highest percentage of Russians (12.9%) of all Canadian ridings (implying the presence of a strong community of Russian Jews).
The Thornhill riding has the highest percentage of population with an educational attainment of "University certificate or diploma above bachelor level" (i.e. above-bachelor-level certificate or diploma other than doctorate, master, or medicine etc. degrees) with 5.0%.