Efficacious "packaged" teen smoking cessation treatment programs, those developed by national organizations, are widely disseminated to local communities to help teens quit smoking. The implementation fidelity of these programs in community settings has not been documented. The efficacy of these programs could be lessened if they are not implemented as intended. Data from Helping Young Smokers Quit describe the frequency and types of modifications made to packaged teen cessation treatment programs for community delivery. A national sample of 591 community-based teen tobacco cessation treatment programs was profiled and 59% used a single packaged treatment program. Bivariate analyses found that 63% of program administrators reported implementing their program as planned; 37% modified their selected program. The most frequently reported modifications were made to the length and format of the program. Of those who modified their programs, greater than 90% reported multiple program modifications (e.g. length and content). Administrators modified their programs to accommodate implementation barriers, such as time constraints and low participant enrollment, and to address the needs of participants with multiple risk behaviors that are co-morbid with tobacco use.