Theoretical research has modelled the existence of so-called advertising-circulation spirals of newspapers. The present article examines the existence and shape of the growth functions of circulation for leading regional newspapers in Finland, and assesses their effects on their competitors. The article also provides results on the household coverage of the regionally leading newspapers. Our results enable us to draw conclusions concerning the level of convergence of the market shares of the larger newspapers, and the possibilities of the minority newspapers to survive. The findings relate directly to the assessment of competition in the market of newspaper publishing, as economic analysis has already shown that difference in size between the two largest firms may define the scope for dominance. Consequently, the results may have implications for assessments of the relevant market and the state of the competition, and claims concerning dominance in newspaper markets.