This chapter presents a commentary on the Handbook of Professional Youth Mentoring from the perspective of program planning. Program evaluation provides a window into the successes and failures of program planning. When the evaluation of a program does not produce the desired results, it is usually due to one or more of the following failures in planning: the design of the program did not consider theory, or the wrong theory was used; the program failed to serve the population that would most likely benefit; there was insufficient contact or program “dosage”; resource problems did not allow the program to be implemented as intended; and/or program outcomes were not clearly articulated and/or were not logically linked to program activities. Several chapters illustrate various ways that youth mentoring programs have failed when important program design elements were not considered. Conversely, other chapters provide testimony to the likelihood of success when youth mentoring programs are well planned, from conceptualization of the problem through to program design and evaluation. The importance of applying” best practice” program planning principles when designing the various facets of youth mentoring programs is discussed.