Purpose To report vascular comorbidities, arterial hypertension (HT), ischemic heart disease (IHD), and diabetes mellitus (DM) in patients with low-tension glaucoma (LTG) with maximum intraocular pressure (IOP) of 18 mm Hg or less. Uniform criteria for glaucoma and the comorbidities were applied. Methods We reviewed records of 519 consecutive patients to whom the Finnish National Social Insurance Institution (FSII) had granted cost-free medication for the treatment of glaucoma. The FSII operates national health insurance, which is compulsory for all Finnish citizens. There were 344 patients with primary open-angle glaucoma (POAG) and 155 with exfoliative glaucoma (EG). Twenty cases were discarded for having other types of glaucoma. In the POAG group, there were 38 patients, with a median IOP of 16 mm Hg (range 12–18). We were masked to the systemic comorbidities when the registry provided us data on those to whom FSII had also granted cost-free medication for HT, IHD, or DM according to the uniform national criteria. Results None of the patients with LTG had exfoliation syndrome. There was a female predominance, 81%, compared to 68% in high-tension POAG. Hypertension had been diagnosed in 34%, which is the same as in high-tension POAG. A total of 24% had IHD, which is the same as in the Finnish population registry. Diabetes mellitus was present in only 5%. In all groups, patients with LTG with systemic comorbidity were markedly older than those without. Conclusions In patients with LTG with median IOP 16 mm Hg (range 12–18), glaucomatous optic disc cupping and glaucomatous visual field defects probably developed independently of the systemic vascular comorbidity. However, the diagnostic criteria for HT, IHD, and DM used in the current study were based on the severity of stages set in the FSII system.