The broadcaster studied the results of cantonal parliamentary elections in the past 15 years and found that women continue to be under-represented.
In the past 15 years the percentage of women elected to cantonal parliaments has plateaued at 27.7 percent on average, though disparities exist between the regions.
The parliaments of Basel-Land and Aargau have the biggest proportion of women, at 37.8 percent and 36.4 percent respectively, while Schwyz brings up the rear, on only 14 percent.
Part of the reason is that women do not present themselves as candidates as often as men, with electoral lists being only 32 percent female on average, said RTS.
However that's not the whole story, since women who do stand for office are less easily elected, found the study.
Of 100 female candidates in recent cantonal parliamentary elections, only 14 percent were elected; that figure stands at 17.6 percent for men.
In the last 15 years only once have women had a better success rate than men, in Neuchâtel's elections last year.
Valais comes out worst, according to the study. In its 2017 elections 27.6 percent of candidates were women, but only 19 percent of those elected were women.
The study also found disparities between political parties.
The Green Party and the Socialists are the closest to achieving parity, with 45 percent of their recent elected cantonal parliamentarians being women. Socialists and Green-Liberal female candidates actually have a better success rate than their male colleagues, said the study.
However parties on the political right have fewer female representatives in cantonal governments, both because they put fewer women forward and because their success rate with the electorate is lower.
The Swiss People's Party (SVP), for example, has had only 17.9 percent women on its electoral lists in recent elections, achieving a success rate of just 13.8 percent.
The proportion of women in cantonal governments – the executive – is no better, with an average of 24 percent of elected councillors being women.
Some cantonal governments, including Lucerne and Ticino, have no women in their executive, said RTS.
Switzerland has a complex relationship with women's political rights.
It was one of the last countries in the developed world to grant women the right to vote and enter politics, holding out until 1971.
The proportion of women in politics rose during the 1980s and 90s, and Switzerland gained its first female president, Ruth Dreifuss, in 1999.
In 2010 the Swiss Federal Council – the federal government's seven-person executive – had more women than men for the first time.
Under Switzerland's rotating presidency, Doris Leuthard is currently the country's president for the second time.