objective: to analyze the reliability and performance of the portuguese version of questionnaires used to evaluate adherence to hypertensive treatment. methods: hypertensive patients attending a primary healthcare unit in porto alegre, southern brazil, from january to september 2010, were randomly selected (n = 206). to evaluate adherence, portuguese versions of the morisky-green test (mgt) and the brief medication questionnaire (bmq) were used. the analysis considered internal consistency, temporal stability and performance compared to three gold standards, which are: inadequate control of blood pressure (bp > 140/90 mmhg); insufficient rate of medication acquisition at the institution's pharmacy (<80%) and a combination of both factors. results: of the patients studied, 97 only used medications dispensed by the basic health unit. the tests showed good internal consistency by cronbach's α: bmq 0.66 (95%ci 0.60 to 0.73) and the mgt 0.73 (95%ci 0.67 to 0.79). the bmq regimen screen had a sensitivity of 77%, specificity of 58%, and an area under the roc curve of 0.70 (95%ci 0.55 to 0.86); for mgt sensitivity was 61%, specificity 36% and area under the roc curve 0.46 (95%ci 0.30 to 0.62). the correlation between the bmq and the mgt was r=0.28, p> 0.001. low adherence per the bmq is associated with higher blood pressure levels when compared to adherent patients (148.4 [sd 20.1] vs 128.8 [sd 17.8]; p <0.001), but not for the mgt. conclusions: the bmq showed better performance than the mgt, with greater sensitivity and specificity. evaluation of adherence may help clinicians discriminate between inadequate use of medication and insufficient treatment regimen.