AIM: To investigate the effectiveness of diquafosol ophthalmic solution 3% administered in Korean patients with dry eye disease in real-world clinical settings. METHODS: Diquafosol was administered for 8wk to 3 patient groups who received diquafosol as add-on therapy to existing medication (Add group, n=150); received diquafosol only (Monotherapy group, n=196); or discontinued part of their existing medication in favor of diquafosol (Switch group, n=11). Tear break-up time (TBUT), cornea and conjunctival staining based on National Eye Institute/Industry scoring scheme, subjective symptoms using the Ocular Surface Disease Index (OSDI) questionnaire, and meibum quality and expressibility were evaluated at baseline, week 4, and week 8. RESULTS: The mean TBUT increased (from 3.46, 3.92, and 5.84s, respectively, to 5.15, 5.53, and 8.59s, respectively) and corneal staining score decreased (from 2.23, 2.24, and 3.09, respectively, to 0.85, 0.97, and 1.64, respectively) in a time-dependent manner from baseline to week 8 in all three groups. Conjunctival staining score, OSDI questionnaire, and meibum quality and expressibility improved over time from baseline to week 8 in the Add and Monotherapy groups, but differences were not statistically significant in the Switch group. CONCLUSION: Diquafosol improves subjective symptoms and objective signs in patients treated with existing medicines combined with diquafosol and treated solely with diquafosol. Diquafosol can be used as an effective therapeutic agent for dry eye disease or additionally applied in patients who have insufficient response to existing medicines.