In nearly all studies on legislative party competition, all votes are treated equally. It is argued in this article that the cooperation between parties varies substantively depending on the type of legislation analysed. However, establishing a measure of the relative significance of votes has challenged legislative studies for decades. A novel measure for legislative significance is therefore proposed: length of debate. Using parliamentary votes from 23 legislative periods in the Danish parliament from 1953 to 2003 and debate length as measurement for bill significance, analyses are presented that focus on between‐party voting patterns on significant and non‐significant legislation and the presence, extent and features of legislative cartels is discussed. The results suggest that looking only at significant legislation reveals more clearly the legislative cartels within the legislature. These findings challenge the traditional assumption of treating parliamentary votes equally, and they allow for a better understanding of legislative cartels in the Folketing.