Objective To assess the clinical value of three-dimensional speckle tracking imaging (3D-STI) in detecting left ventricular systolic function in patients with paroxysmal atrial fibrillation (PAF).Methods 34 patients with PAF and 34 matched subjects were included.The strains of the left ventricular 17 segments (longitudinal and radial strain) were acquired using 3D-STI.Results Compared with the controls,the strains were decreased in the posterior wall,the inferior wall and the posterior septum below the left ventricular papillary muscle level in the PAF group,the differences were statistically significant (P ＜ 0.05),while there were no significant differences in other segments (P ＞ 0.05).Conclusions Left ventricular systolic function in patients with PAF was decreased,but the decreased degree of the segments was not all the same.3D-STI can evaluate left ventricular systolic function in patients with PAF and provide valuable clinical information.