To have faith, confidence, or belief in someone or something; to care about, appreciate, or respect someone or something. It is important that one sets store by one's friends, for it is to them one must turn when life becomes difficult. My brother is not one to set store by obeying social rules or etiquette.
Also, set great store by. Regard as valuable or worthwhile, as in I don't set much store by her judgment, or He sets great store by his good name. The word store here is used in the sense of "something precious," a usage that is obsolete except in these terms.
consider something to be of a particular degree of importance or value.