Objective: The aim of this study was to evaluate the healing responses following surgical or repeated non-surgical treatment in residual pockets of previously non-surgically treated periodontitis patients. Methods: 12 female and 4 male subjects (mean age = 44.5 years) were recruited for this split-mouth, single-blinded study. Matched-paired-sites with residual probing pocket depth ≥6mm and bleeding on probing were selected in each patient. Presence of supragingival plaque (Pl%), bleeding on probing (BOP%), probing pocket depth (PPD) and probing attachment level (PAL) were recorded at baseline and 3 months after treatment. Test sites were selected randomly for repeated non-surgical debridement under local anaesthesia while control sites received surgical treatment. Results: Full-mouth Pl% decreased from 20% at baseline to 17% at 3 months and the BOP% decreased from 25% to 22%. Mean PPD reduction for test and control sites were 3.3mm and 3.1mm (p>0.05, paired t-test), mean PAL gains were 2.5mm and 1.7mm (p>0.05), and mean increases in recession were 0.8mm and 1.4mm (p<0.05). Conclusion: The healing responses in residual periodontally-involved sites following non-surgical or surgical treatment were similar and both treatment modalities were effective in PPD reduction and gain of PAL, but surgical debridement caused more recession.