The current report is part of a prospective, multi-center, two-arm, quasi-randomized field study focusing on the effectiveness in general praxis of evidence-based procedures in the non-surgical treatment of patients with periodontitis. The specific aims were to (i) evaluate patient-reported experience and outcome measures of treatment following a guided approach to periodontal infection control (GPIC) compared to conventional non-surgical therapy (CNST) and to (ii) identify potential predictors of subjective treatment outcomes and patient's adherence to self-performed infection control, i.e. adequate oral hygiene. The study sample consisted of 494 patients treated per protocol with questionnaire- and clinical data at baseline and 6-months. The GPIC approach (test) comprised patient education for adequate oral hygiene prior to a single session of full-mouth ultra-sonic instrumentation, while the CNST approach (control) comprised education and instrumentation (scaling and root planing) integrated at required number of consecutive appointments. Clinical examinations and treatment were performed by Dental Hygienists, i.e. not blinded. Data were processed with bivariate statistics for comparison between treatment groups and with multiple regression models to identify potential predictors of subjective and clinical outcomes. The primary clinical outcome was gingival bleeding scores. No substantial differences were found between the two treatment approaches regarding patient-reported experiences or outcomes of therapy. Patients' experiences of definitely being involved in therapy decisions was a significant predictor for a desirable subjective and clinical outcome in terms of; (i) that oral health was considered as much improved after therapy compared to how it was before, (ii) that the treatment definitively had been worth the cost and efforts, and (iii) adherence to self-performed periodontal infection control. In addition, to be a current smoker counteracted patients' satisfaction with oral health outcome, while gingival bleeding scores at baseline predicted clinical outcome in terms of bleeding scores at 6-months. The results suggest that there are no differences with regard to patient-reported experiences and outcomes of therapy following a GPIC approach to periodontal infection control versus CNST. Patients' experiences of being involved in therapy decisions seem to be an important factor for satisfaction with care and for adherence to self-performed periodontal infection control. Registered at: ClinicalTrials.gov (NCT02168621).