Background The purpose of the study was to estimate the heritability of leukocyte telomere length (LTL) and lung function and to examine whether LTL and lung function share genetic or environmental effects in common. Methods 386 monozygotic and dizygotic Finnish twin sisters (age 68.4±3.4 years) were included. Relative LTL was determined from peripheral blood DNA by qPCR. Lung function measures of FEV1, FVC, FEV1/FVC, and PEF were derived from spirometry. Genetic modeling was performed with MPlus statistical software. Results Univariate analysis revealed that in LTL, 62% (95% confidence interval 50–72) of the variance was explained by additive genetic and 38% (28–50) by unique environmental factors. For FEV1, FVC, and PEF, the corresponding estimates were 65%–67% for additive genetic and 33%–35% for unique environmental factors. Across the sample, the phenotypic correlation between LTL and FEV1 was modest (r = .104, p = .041). Bivariate correlated factors model revealed that the genetic correlation between LTL and FEV1 was .18 (−0.19 to 0.64) and environmental correlation was −.10 (−0.84 to 0.55). Conclusions Both LTL and lung function variables are moderately to highly genetically determined. The associations between LTL and the lung function variables were weak. However, the positive genetic correlation point estimate gave minor suggestions that, in a larger sample, genetic factors in common might play a role in the phenotypic correlation between LTL and FEV1. Future studies with larger samples are needed to confirm these preliminary findings.