The Collaborative International Dictionary of English v.0.48:

Dutiful \Du"ti*ful\, a.
   1. Performing, or ready to perform, the duties required by
      one who has the right to claim submission, obedience, or
      deference; submissive to natural or legal superiors;
      obedient, as to parents or superiors; as, a dutiful son or
      daughter; a dutiful ward or servant; a dutiful subject.
      [1913 Webster]

   2. Controlled by, proceeding from, a sense of duty;
      respectful; deferential; as, dutiful affection.

   Syn: Duteous; obedient; reverent; reverential; submissive;
        docile; respectful; compliant. -- Du"ti*ful*ly, adv.
        -- Du"ti*ful*ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

dutiful
    adj 1: willingly obedient out of a sense of duty and respect; "a
           dutiful child"; "a dutiful citizen"; "Patient Griselda
           was a chaste and duteous wife"; [syn: dutiful,
           duteous]

Moby Thesaurus II by Grady Ward, 1.0:

65 Moby Thesaurus words for "dutiful":
   Christian, Christianlike, Christianly, accommodating, acquiescent,
   active, adoring, attentive, believing, cap in hand, ceremonious,
   compliant, complying, conforming, conscientious, considerate,
   constant, courteous, cultish, cultist, cultistic, deferential,
   devoted, devout, diligent, duteous, ethical, faithful, filial,
   flexible, honorific, law-abiding, loyal, malleable, meticulous,
   mindful, moral, obedient, obliging, observant, pietistic, pious,
   pliant, polite, practicing, prayerful, punctilious, punctual,
   regardful, reliable, religious, respectful, responsible, reverent,
   reverential, scrupulous, solemn, submissive, theistic, true,
   venerational, venerative, willing, worshipful, yielding