Since the Gospel of Thomas was first discovered, scholars have been divided on whether the gospel was written in the second century or early in the first century. One view is based on the assumption that gnosticism could not have existed before about the second century, because Christian doctrine could not have split into two distinct streams so soon after the death of Jesus. The view that the Gospel of Thomas was written early in the first century, around the same time as 'Q' is dominant among American scholars and is based on the relatively primitive nature of GThomas, its similarity to Q and it lack of any mention of the crucifixion. Stephen J.Patterson says in The Gospel of Thomas and Jesus, pp. 116-117:
The text thus dates to a period in which authority was still personal, or dependent upon a leader's personal charisma and powers of persuasion, and not yet apostolic properly speaking . . . All of this would suggest a date close to Paul. . . or to Mark.
The Q Gospel was certainly written in Greek, as can be established by comparing the occurrences of Q material in Matthew and Luke. The similarities between GThomas and Q demonstrate that GThomas was also written in Greek, and that they probably share a common source, also in the Greek language.
Those similarities are not close enough for GThomas actually to be Q, although it was hoped to be when first discovered. Even when material in GThomas is similar to material in Q, it does not occur in the same sequence as in Q. GThomas is mildly gnostic, with no hint of apocalypticism; Q is mildly apocalyptic, especially in its later stages, with no hint of gnosticism as we understand it.