Most randomized controlled clinical trials regarding the effects of non-surgical periodontal treatment have focused on objective parameters. Their effects on patient-centered variables have been received very little attention. After determining clinical therapeutic efficacy, this study compared over 6 months the effects of two different forms of non-surgical periodontal therapy - scaling and root planing per quadrant (SRP) and one-stage full-mouth disinfection (FMD) - on scores of quality of life, fear, anxiety and pain of moderate chronic periodontitis. Initially, the sample size was calculated considering protocols' clinical efficacy. Specifically for the present study it was verified if the initial sample size would be enough for analysis of the subjective variables.