The age structure of Scots pine (Pinus sylvestris L.) bog woodland was investigated at four sites in NE Scotland to clarify whether these examples of the habitat are stable or transient. Individual tree age cannot be predicted from general equations relating age to height or diameter. The sampling sites at Pitmaduthy Moss, Abernethy Forest and Inshriach Forest had been severely impacted by human activities, some of which were reflected in the age structure of the pine population. Most of the Monadh Mor site was apparently undisturbed. The site at Abernethy Forest supported ‘bog pines’ up to 335 years old and a ground flora including Sphagnum fuscum and abundant Sphagnum austinii. This combination suggests that the site has supported open bog woodland for several centuries. These results are consistent with a process of bog woodland development on bogs in response to natural or anthropogenic disturbance. Tree growth rates and branching may be used as indicators of the degree of alteration caused by the disturbance and of whether the site is likely to succeed to closed-canopy woodland.