It is essential for school psychologists assessing children to use instruments that are reliable and valid. The focus of the current study is to determine whether or not the parent preschool versions of two popular behavior rating instruments, the Behavior Assessment System for Children – Second Edition (BASC-2; Reynolds & Kamphaus, 2004) and Child Behavior Checklist (CBCL; Achenbach & Rescorla, 2000), are consistent measures of similarly-named behavioral constructs in preschool-aged children. Parents of 95 preschoolers referred to a nonprofit child evaluation clinic because of behavioral or developmental concerns completed both the BASC-2 and CBCL during an initial evaluation session. The findings revealed that while significantly high correlations occurred, the mean standard scores were significantly different for nine of the 15 construct comparisons. For six of the 15 comparisons, the mean difference was greater than one standard deviation. Additionally, the CBCL usually resulted in higher ratings than the BASC-2. Such findings imply that the two instruments are not equivalent, and results from these two behavior rating scales need to be interpreted with caution. The determination of whether or not a construct is considered clinically significant may depend solely on the instrument completed by the parent.