To evaluate left atrial (LA) volume and function as assessed by strain and strain rate derived from 2D speckle tracking and their association with diastolic dysfunction (DD) in patients with diabetes mellitus (DM).Seventy three patients with DM were compared with age- and gender-matched normal controls; 30 patients with DM alone were compared to those with hypertension (HT) alone. The maximum LA volume, traditional measures of atrial function, 2D strain and strain rate were analysed. The LA indexed volume (LAVI) was larger in DM group than that in normal controls (38.2 ± 9.9 vs. 20.5 ± 4.8 ml/m(2), P< 0.0001), as well as in DM alone compared with hypertensive patients (33.9 ± 10 vs. 25.7 ± 8 ml/m(2), P< 0.0001). Global strain was significantly reduced in the DM group compared with that in normal controls (22.5 ± 8.67 vs. 30.6 ± 8.27%; P< 0.0001) but was similar with HT. There was a weak correlation between LAVI and global strain with increasing grades of DD (r= 0.439, P< 0.0001 and r= - 0.316, P< 0.0001, respectively) in the diabetic group. However, there was no significant difference in LAVI between these groups. A logistic regression analysis for predictors of LAVI demonstrated that only diabetes was a determinant of LAVI. Patients with diabetes showed a significant reduction in global strain compared with normal controls but no difference with increasing grades of diastolic function.LA enlargement in DM is independent of associated HT and diastolic function. LA enlargement is associated with LA dysfunction as evaluated by 2D strain. It is likely that a combination of DD and a diabetic atrial myopathy contribute to LA enlargement in patients with DM.