Directly measured growth rates of two lichens (Pseudephebe minuscula and Rhizocarpon sections Rhizocarpon and Superficiale) from Svalbard made over a two-decade interval (1984–2007) are presented. Growth rates were determined by measuring the change in area of the lichen thalli from digital images and converting area to diameter. Pseudephebe diameter growth rates ranged from 0.2 to 1.5 mm yr⁻¹ and Rhizocarpon grew 0.05 to 0.30 mm yr⁻¹. Growth rates of both are a function of thalli size—growth rates increase with increasing thallus size up to 70 mm diameter for Pseudephebe and 30 mm diameter for Rhizocarpon. While these directly measured growth rate results are consistent with other recent directly measured lichen growth studies, they are not consistent with indirectly determined age-size curves that show a negative correlation between size and growth rate (i.e., rapid “great growth” followed by slower “linear growth”). We explore several reasons to explain the apparent discrepancy between directly measured and indirectly determined growth rates, including climate change, increased nutrient fluxes, and population sampling differences between the two methods. We argue that indirectly determined growth curves, which integrate the effects of changing growing conditions over time, remain the best basis for lichenometric dating.