The dandelion may be confused with catsears (Hypochaeris) hawksbeards (Crepis)
and hawksweeds (Hyeracium) as the flower and leaf can appear to be slightly
similar. Once you get used to identifying the leaf it becomes quite easy to tell them apart.
However the flower stem is the most obvious distinguishing feature
on a Dandelion
which has a hollow, smooth, single stem for each flower. On similar species
the stem is solid and branched often with hairs or leaflets upon it.
Thankfully none of these species are considered poisonous, however always positively identify any plant before use.